diff --git a/README.md b/README.md
index 5b03c22..59e0d10 100644
--- a/README.md
+++ b/README.md
@@ -20,8 +20,9 @@ MegFlow 提供快速视觉应用落地流程，最快 15 分钟搭建起视频
   * [build on win10](docs/how-to-build-and-run/build-on-win10.zh.md)
   * [generate rtsp](docs/how-to-build-and-run/generate-rtsp.zh.md)
 * how to use
-  * [add my first service](docs/how-to-add-my-service/01-single-classification-model.zh.md)
-  * [how to optimize and debug](docs/how-to-debug.zh.md)
+  * [tutorial01: image classification service](docs/how-to-add-my-service/01-single-classification-model.zh.md)
+  * [tutorial02: detect and classify on video stream](docs/how-to-add-my-service/02-single-det-classify.zh.md)
+* [how to debug](docs/how-to-debug.zh.md)
 * [how to contribute](docs/how-to-contribute.zh.md)
 * [FAQ](docs/FAQ.zh.md)
 
diff --git a/ci/run_pylint_check.sh b/ci/run_pylint_check.sh
index 7434b65..be0de0a 100755
--- a/ci/run_pylint_check.sh
+++ b/ci/run_pylint_check.sh
@@ -1,5 +1,5 @@
 python -m pip install pylint==2.5.2
-CHECK_DIR="flow-python/examples/simple_classification flow-python/examples/cat_finder flow-python/examples/electric_bicycle"
+CHECK_DIR="flow-python/examples/simple_classification flow-python/examples/simple_det_classify flow-python/examples/cat_finder flow-python/examples/electric_bicycle"
 pylint $CHECK_DIR || pylint_ret=$?
 if [ "$pylint_ret" ]; then
     exit $pylint_ret
diff --git a/docs/how-to-add-my-service/01-single-classification-model.zh.md b/docs/how-to-add-my-service/01-single-classification-model.zh.md
index 3cfa6c0..8650a58 100644
--- a/docs/how-to-add-my-service/01-single-classification-model.zh.md
+++ b/docs/how-to-add-my-service/01-single-classification-model.zh.md
@@ -17,7 +17,7 @@ $ python3 dump.py
 $ ls -lah model.mge
 ...
 ```
-`dump.py` 正在 PR 到 MegEngine/models
+`dump.py` 已经 PR 到 [MegEngine/models 分类模型目录](https://github.com/MegEngine/Models/tree/master/official/vision/classification)
 ```bash
 $ cat dump.py
 ...
@@ -125,20 +125,49 @@ class Classify:
 * `__init__` 里加载模型，做个 warmup 防止首次推理太慢
 * 解码成 BGR 的 data 在 `envelope.msg['data']`，推理，send 返回 json string
 
-[更多 node 说明](appendix-B-python-plugin.zh.md)
+[classify.py 各参数说明](appendix-B-python-plugin.zh.md)
 
 ## 运行测试
 
 运行服务
 ```bash
 $ cd flow-python/examples
-$ run_with_plugins -c simple_classification/image_cpu.toml  -p  simple_classification # 源码/docker 编译方式用这条命令
+$ run_with_plugins -c simple_classification/image_cpu.toml  -p  simple_classification
 ```
 
-浏览器打开 8084 端口服务（例如 http://10.122.101.175:8084/docs ），选择一张图“try it out”即可。
+### WebUI 方式
+浏览器打开 8084 端口服务（例如 http://127.0.0.1:8084/docs ），选择一张图“try it out”即可。
 
-## 其他
+### 命令行方式
+```bash
+$ curl http://127.0.0.1:8081/analyze/image_name  -X POST --header "Content-Type:image/*"   --data-binary @test.jpeg
+```
+
+`image_name` 是用户自定义参数，用在需要 POST 内容的场景。这里随便填即可；`test.jpeg` 是测试图片
+
+### Python Client
+
+```Python
+$ cat ${MegFlow_DIR}/flow-python/examples/simple_classification/client.py
 
-一、http 客户端开发
+import requests
+import cv2
+
+def test():
+    ip = 'localhost'
+    port = '8084'
+    url = 'http://{}:{}/analyze/any_content'.format(ip, port)
+    img = cv2.imread("./test.jpg")
+    _, data = cv2.imencode(".jpg", img)
+    data = data.tobytes()
+
+    headers = {'Content-Length': '%d' % len(data), 'Content-Type': 'image/*'}
+    res = requests.post(url, data=data, headers=headers)
+    print(res.content)
+
+if __name__ == "__main__":
+    test()
+```
 
-rweb/Swagger 提供了 http RESTful API 描述文件，例如在 http://10.122.101.175:8084/openapi.json 。`swagger_codegen` 可用描述文件生成各种语言的调用代码。更多教程见 [swagger codegen tutorial ](https://swagger.io/tools/swagger-codegen/)。
+### 其他语言
+rweb/Swagger 提供了 http RESTful API 描述文件，例如在 http://127.0.0.1:8084/openapi.json 。`swagger_codegen` 可用描述文件生成 java/go 等语言的调用代码。更多教程见 [swagger codegen tutorial ](https://swagger.io/tools/swagger-codegen/)。
diff --git a/docs/how-to-add-my-service/02-single-det-classify.zh.md b/docs/how-to-add-my-service/02-single-det-classify.zh.md
new file mode 100644
index 0000000..ec5b3a2
--- /dev/null
+++ b/docs/how-to-add-my-service/02-single-det-classify.zh.md
@@ -0,0 +1,147 @@
+# 串连检测和分类
+
+本文将在 [tutorial01](01-single-classification-model.zh.md) 的基础上扩展计算图：先检测、再扣图分类。对外提供视频解析服务。完整的代码在 [simple_det_classify](../../flow-python/examples/simple_det_classify) 。
+
+## 移除分类预处理
+
+之前提到过：MegEngine 除了不需要转模型，还能消除预处理。我们修改 `dump.py` 把预处理从 SDK/业务代码提到模型内。这样的好处是：**划清工程和算法的边界**，预处理本来就应该由 scientist 维护，每次只需要 release mge 文件，减少交接内容
+
+```bash
+$ cat ${MegFlow}/flow-python/examples/simple_det_classify/dump.py
+...
+    data = mge.Tensor(np.ones(shape, dtype=np.uint8))
+
+    @jit.trace(capture_as_const=True)
+    def pred_func(data):
+        out = data.astype(np.float32)
+        # resnet18 预处理
+        output_h, output_w = 224, 224
+        # resize
+        M = mge.tensor(np.array([[1,0,0], [0,1,0], [0,0,1]], dtype=np.float32).reshape((1,3,3)))
+        out = F.vision.warp_perspective(out, M, (output_h, output_w), format='NHWC')
+        # mean
+        _mean = mge.Tensor(np.array([103.530, 116.280, 123.675], dtype=np.float32))
+        out = F.sub(out, _mean)
+        # div 
+        _div = mge.Tensor(np.array([57.375, 57.120, 58.395], dtype=np.float32))
+        out = F.div(out, _div)
+        # dimshuffile 
+        out = F.transpose(out, (0,3,1,2))
+
+        outputs = model(out)
+        return outputs
+...
+```
+具体实现是在 trace inference 里增加预处理动作，fuse opr 优化加速的事情交给 MegEngine 即可。更多 cv 操作参照 [MegEngine API 文档](https://megengine.org.cn/doc/stable/zh/reference/api/megengine.functional.vision.warp_perspective.html?highlight=warp_perspective)。
+
+因为推理输入变成了 BGR，所以 dump 模型的时候参数也应该跟着变
+```bash
+$ python3 dump.py -a resnet18 -s 1 224 224 3 
+```
+
+## 准备检测模型
+这里直接用现成的 YOLOX mge 模型。复用 [cat_finder 的检测](../../flow-python/examples/cat_finder/det.py) 或者从 [YOLOX 官网](https://github.com/Megvii-BaseDetection/YOLOX/tree/main/demo/MegEngine/python) 下载最新版。
+
+##  配置计算图
+`flow-python/examples` 增加 `simple_det_classify/video_cpu.toml`
+
+```bash
+$ cat flow-python/examples/simple_det_classify/video_cpu.toml
+
+main = "tutorial_02"
+
+# 重资源结点要先声明
+[[nodes]]
+name = "det"
+ty = "Detect"
+model = "yolox-s"
+conf = 0.25
+nms = 0.45
+tsize = 640
+path = "models/simple_det_classify_models/yolox_s.mge"
+interval = 5
+visualize = 1
+device = "cpu"
+device_id = 0
+
+[[nodes]]
+name = "classify"
+ty = "Classify"
+path = "models/simple_det_classify_models/resnet18_preproc_inside.mge"
+device = "cpu"
+device_id = 0
+
+[[graphs]]
+name = "subgraph"
+inputs = [{ name = "inp", cap = 16, ports = ["det:inp"] }]
+outputs = [{ name = "out", cap = 16, ports = ["classify:out"] }]
+# 描述连接关系
+connections = [
+  { cap = 16, ports = ["det:out", "classify:inp"] },
+]
+
+...
+# ty 改成 VdieoServer
+    [[graphs.nodes]]
+    name = "source"
+    ty = "VideoServer"
+    port = 8085
+    
+...
+```
+想对上一期的配置，需要关注 3 点：
+* 视频流中的重资源结点，需要声明在  `[[graphs]]` 之外，因为多路视频需要复用这个结点。如果每一路都要启一个 det 结点，资源会爆掉
+* `connections` 不再是空白，因为两个结点要描述连接关系
+* Server 类型改成 `VideoServer`，告诉 UI 是要处理视频的
+
+## 实现细节
+* 可以看到此时 [resnet18 的 lite.py](../../flow-python/examples/simple_det_classify/lite.py) 已经删除了 preprocess 函数
+* det.py 可以直接用 `cat_finder` 的
+
+## 运行测试
+
+运行服务
+```bash
+$ cd flow-python/examples
+$ run_with_plugins -c simple_det_classify/video_cpu.toml  -p simple_det_classify
+```
+
+### WebUI 方式
+浏览器打开 8085 端口服务（例如 http://127.0.0.1:8085/docs ）
+
+* 参照 [如何生成 rtsp](../how-to-build-and-run/generate-rtsp.zh.md)，提供一个 rtsp 流地址
+* 或者干脆给 .mp4 文件的绝对路径（文件和 8085 服务在同一台机器上）
+
+### 命令行方式
+```bash
+$ curl  -X POST  'http://127.0.0.1:8085/start/rtsp%3A%2F%2F127.0.0.1%3A8554%2Ftest1.ts'  # start  rtsp://127.0.0.1:8554/test1.ts
+start stream whose id is 2% 
+$ curl 'http://127.0.0.1:8085/list'   # list all stream
+[{"id":1,"url":"rtsp://10.122.101.175:8554/test1.ts"},{"id":0,"url":"rtsp://10.122.101.175:8554/test1.ts"}]%
+```
+路径中的 `%2F`、`%3A` 是 [URL](https://www.ietf.org/rfc/rfc1738.txt) 的转义字符
+
+### Python Client
+
+```Python
+$ cat ${MegFlow_DIR}/flow-python/examples/simple_det_classify/client.py
+
+import requests
+import urllib
+
+
+def test():
+    ip = 'localhost'
+    port = '8085'
+    video_path = 'rtsp://127.0.0.1:8554/vehicle.ts'
+    video_path = urllib.parse.quote(video_path, safe='')
+    url = 'http://{}:{}/start/{}'.format(ip, port, video_path)
+
+    res = requests.post(url)
+    ret = res.content
+    print(ret)
+
+
+if __name__ == "__main__":
+    test()
+```
diff --git a/docs/how-to-build-and-run/build-from-source.zh.md b/docs/how-to-build-and-run/build-from-source.zh.md
index 4f65608..36f2926 100644
--- a/docs/how-to-build-and-run/build-from-source.zh.md
+++ b/docs/how-to-build-and-run/build-from-source.zh.md
@@ -80,7 +80,7 @@ P.S. 默认 ffmpeg 依赖自动从 github 上拉取源码构建，这会使得
 ```bash
 $ cd examples
 $ cargo build --example run_with_plugins --release # 编译出 megflow bin
-$ ln -s ../../target/example/run_with_plugins
+$ ln -s ../../target/release/examples/run_with_plugins
 $ ./run_with_plugins -p logical_test
 ```
 `logical_test` 是 examples 下最基础的计算图测试用例，运行能正常结束表示 MegFlow 编译成功、基本语义无问题。
diff --git a/docs/how-to-debug.zh.md b/docs/how-to-debug.zh.md
index 4e768b5..4a291df 100644
--- a/docs/how-to-debug.zh.md
+++ b/docs/how-to-debug.zh.md
@@ -1 +1,12 @@
-# 
\ No newline at end of file
+# 如何 Debug 常见问题
+
+一、`run_with_plugins` 无法启动服务，直接 core dump 报错退出
+
+如果“Python 开机自检”的  `run_with_plugins -p logical_test` 能够正常结束，排查方向应该是 Python import error。调试方法举例
+```bash
+$  gdb --args ./run_with_plugins  -c electric_bicycle/electric_bicycle_cpu.toml   -p electric_bicycle
+...
+illegal instruction
+...
+```
+可以看到 crash 发生在哪个 import
\ No newline at end of file
diff --git a/flow-python/examples/cat_finder/README.md b/flow-python/examples/cat_finder/README.md
index eb189b9..3349bba 100644
--- a/flow-python/examples/cat_finder/README.md
+++ b/flow-python/examples/cat_finder/README.md
@@ -1,7 +1,7 @@
 # 猫猫围栏
 
 ## 一、功能概述
-注册的猫猫离开围栏，会收到一条告警信息。未注册的不会报警。
+注册的猫猫离开围栏，会收到一条告警信息。未注册的不会报警。 CPU 配置已提供，没有 GPU 也可以运行。
 
 ## 二、模型和自测数据下载
 
diff --git a/flow-python/examples/simple_classification/client.py b/flow-python/examples/simple_classification/client.py
new file mode 100644
index 0000000..4b3394e
--- /dev/null
+++ b/flow-python/examples/simple_classification/client.py
@@ -0,0 +1,30 @@
+# MegFlow is Licensed under the Apache License, Version 2.0 (the "License")
+#
+# Copyright (c) 2019-2021 Megvii Inc. All rights reserved.
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT ARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+
+#!/usr/bin/env python
+# coding=utf-8
+import cv2
+import requests
+
+
+def test():
+    ip = 'localhost'
+    port = '8084'
+    user_define_string = 'content'
+    url = f'http://{ip}:{port}/analyze/{user_define_string}'
+    img = cv2.imread("./test.jpg")
+    _, data = cv2.imencode(".jpg", img)
+    data = data.tobytes()
+
+    headers = {'Content-Length': f'{len(data)}', 'Content-Type': 'image/*'}
+    res = requests.post(url, data=data, headers=headers)
+    print(res.content)
+
+
+if __name__ == "__main__":
+    test()
diff --git a/flow-python/examples/simple_classification/lite.py b/flow-python/examples/simple_classification/lite.py
index 034a7c4..68b27c9 100644
--- a/flow-python/examples/simple_classification/lite.py
+++ b/flow-python/examples/simple_classification/lite.py
@@ -1,6 +1,13 @@
-#!/usr/bin/env python3
-# -*- coding:utf-8 -*-
-# Copyright (c) Megvii, Inc. and its affiliates.
+# MegFlow is Licensed under the Apache License, Version 2.0 (the "License")
+#
+# Copyright (c) 2019-2021 Megvii Inc. All rights reserved.
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT ARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+
+#!/usr/bin/env python
+# coding=utf-8
 
 import argparse
 import cv2
diff --git a/flow-python/examples/simple_det_classify/__init__.py b/flow-python/examples/simple_det_classify/__init__.py
new file mode 100644
index 0000000..f57558f
--- /dev/null
+++ b/flow-python/examples/simple_det_classify/__init__.py
@@ -0,0 +1,10 @@
+# MegFlow is Licensed under the Apache License, Version 2.0 (the "License")
+#
+# Copyright (c) 2019-2021 Megvii Inc. All rights reserved.
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT ARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+
+#!/usr/bin/env python
+# coding=utf-8
diff --git a/flow-python/examples/simple_det_classify/classify.py b/flow-python/examples/simple_det_classify/classify.py
new file mode 100644
index 0000000..1cfc848
--- /dev/null
+++ b/flow-python/examples/simple_det_classify/classify.py
@@ -0,0 +1,72 @@
+# MegFlow is Licensed under the Apache License, Version 2.0 (the "License")
+#
+# Copyright (c) 2019-2021 Megvii Inc. All rights reserved.
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT ARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+
+#!/usr/bin/env python
+# coding=utf-8
+
+import json
+import numpy as np
+from loguru import logger
+from megflow import register
+
+from .lite import PredictorLite
+
+
+@register(inputs=['inp'], outputs=['out'])
+class Classify:
+    def __init__(self, name, arg):
+        logger.info("loading Resnet18 Classification...")
+        self.name = name
+
+        # load ReID model and warmup
+        self._model = PredictorLite(path=arg['path'],
+                                    device=arg['device'],
+                                    device_id=arg['device_id'])
+        warmup_data = np.zeros((224, 224, 3), dtype=np.uint8)
+        self._model.inference(warmup_data)
+        logger.info("Resnet18  loaded.")
+
+    def expand(self, box, max_w, max_h, ratio):
+        l = box[0]
+        r = box[2]
+        t = box[1]
+        b = box[3]
+        center_x = (l + r) / 2
+        center_y = (t + b) / 2
+        w_side = (r - l) * ratio / 2
+        h_side = (b - t) * ratio / 2
+
+        l = center_x - w_side
+        r = center_x + w_side
+        t = center_y - h_side
+        b = center_y + h_side
+        l = max(0, l)
+        t = max(0, t)
+        r = min(max_w, r)
+        b = min(max_h, b)
+        return int(l), int(t), int(r), int(b)
+
+    def exec(self):
+        envelope = self.inp.recv()
+        if envelope is None:
+            return
+
+        data = envelope.msg['data']
+        items = envelope.msg['items']
+        results = []
+        for _, item in enumerate(items):
+            assert 'bbox' in item
+            bbox = item['bbox']
+            l, t, r, b = self.expand(bbox, data.shape[1], data.shape[0], 1.1)
+            _type = self._model.inference(data[t:b, l:r])
+            results.append({
+                "type": str(_type),
+                "frame_id": str(envelope.partial_id)
+            })
+
+        self.out.send(envelope.repack(json.dumps(results)))
diff --git a/flow-python/examples/simple_det_classify/client.py b/flow-python/examples/simple_det_classify/client.py
new file mode 100644
index 0000000..22ba281
--- /dev/null
+++ b/flow-python/examples/simple_det_classify/client.py
@@ -0,0 +1,28 @@
+# MegFlow is Licensed under the Apache License, Version 2.0 (the "License")
+#
+# Copyright (c) 2019-2021 Megvii Inc. All rights reserved.
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT ARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+
+#!/usr/bin/env python
+# coding=utf-8
+import urllib
+import requests
+
+
+def test():
+    ip = 'localhost'
+    port = '8085'
+    video_path = 'rtsp://127.0.0.1:8554/vehicle.ts'
+    video_path = urllib.parse.quote(video_path, safe='')
+    url = 'http://{}:{}/start/{}'.format(ip, port, video_path)
+
+    res = requests.post(url)
+    ret = res.content
+    print(ret)
+
+
+if __name__ == "__main__":
+    test()
diff --git a/flow-python/examples/simple_det_classify/det.py b/flow-python/examples/simple_det_classify/det.py
new file mode 100644
index 0000000..60a1d38
--- /dev/null
+++ b/flow-python/examples/simple_det_classify/det.py
@@ -0,0 +1,78 @@
+# MegFlow is Licensed under the Apache License, Version 2.0 (the "License")
+#
+# Copyright (c) 2019-2021 Megvii Inc. All rights reserved.
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT ARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+
+#!/usr/bin/env python
+# coding=utf-8
+
+import numpy as np
+from loguru import logger
+from megflow import register
+from warehouse.detection_yolox import PredictorLite
+
+
+@register(inputs=['inp'], outputs=['out'])
+class Detect:
+    def __init__(self, name, args):
+        logger.info("loading YOLOX detection...")
+        self._tsize = args['tsize']
+        self._interval = args['interval']
+        self._visualize = args['visualize']
+        self.name = name
+
+        # load detect model and warmup
+        self._predictor = PredictorLite(path=args['path'],
+                                        confthre=args['conf'],
+                                        nmsthre=args['nms'],
+                                        test_size=(self._tsize, self._tsize),
+                                        device=args['device'],
+                                        device_id=args['device_id'])
+        warmup_data = np.zeros((224, 224, 3), dtype=np.uint8)
+        self._predictor.inference(warmup_data)
+        logger.info(" YOLOX loaded.")
+
+    @staticmethod
+    def restrict(val, min, max):
+        assert min < max
+        if val < min:
+            val = min
+        if val > max:
+            val = max
+        return val
+
+    def exec(self):
+        envelope = self.inp.recv()
+        if envelope is None:
+            return
+
+        msg = envelope.msg
+        msg['items'] = []
+
+        process = envelope.partial_id % self._interval == 0
+        if process:
+            data = msg['data']
+            outputs = self._predictor.inference(data)
+            # skip if detect nothing
+            if outputs is not None:
+                items = []
+
+                for i in range(outputs.shape[0]):
+                    output = outputs[i]
+                    item = dict()
+                    item["bbox"] = output[0:4]
+                    item["det_score"] = output[4] * output[5]
+                    items.append(item)
+                msg['items'] = items
+
+                # import cv2
+                # x = self._predictor.visual(outputs, data)
+                # name = 'frame{0:07d}.jpg'.format(envelope.partial_id)
+                # cv2.imwrite(name, x)
+
+            if self._visualize == 1:
+                msg['data'] = self._predictor.visual(outputs, data)
+            self.out.send(envelope)
diff --git a/flow-python/examples/simple_det_classify/dump.py b/flow-python/examples/simple_det_classify/dump.py
new file mode 100644
index 0000000..acae30f
--- /dev/null
+++ b/flow-python/examples/simple_det_classify/dump.py
@@ -0,0 +1,97 @@
+# -*- coding: utf-8 -*-
+# MegEngine is Licensed under the Apache License, Version 2.0 (the "License")
+#
+# Copyright (c) 2014-2021 Megvii Inc. All rights reserved.
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT ARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+
+# pylint: skip-file
+import argparse
+import sys
+
+# pylint: disable=import-error
+import resnet.model as resnet_model
+# pylint: disable=import-error
+import shufflenet.model as snet_model
+
+import numpy as np
+
+import megengine as mge
+import megengine.functional as F
+from megengine import jit
+
+
+def dump_static_graph(model, graph_name, shape):
+    model.eval()
+
+    data = mge.Tensor(np.ones(shape, dtype=np.uint8))
+
+    @jit.trace(capture_as_const=True)
+    def pred_func(data):
+        out = data.astype(np.float32)
+
+        output_h, output_w = 224, 224
+        # resize
+        M = mge.tensor(np.array([[1,0,0], [0,1,0], [0,0,1]], dtype=np.float32).reshape((1,3,3)))
+        out = F.vision.warp_perspective(out, M, (output_h, output_w), format='NHWC')
+        # mean
+        _mean = mge.Tensor(np.array([103.530, 116.280, 123.675], dtype=np.float32))
+        out = F.sub(out, _mean)
+        # div 
+        _div = mge.Tensor(np.array([57.375, 57.120, 58.395], dtype=np.float32))
+        out = F.div(out, _div)
+        # dimshuffile 
+        out = F.transpose(out, (0,3,1,2))
+
+        outputs = model(out)
+        return outputs
+
+    pred_func(data)
+    pred_func.dump(
+        graph_name,
+        arg_names=["data"],
+        optimize_for_inference=True,
+        enable_fuse_conv_bias_nonlinearity=True,
+    )
+
+
+def main():
+    parser = argparse.ArgumentParser(description="MegEngine Classification Dump .mge")
+    parser.add_argument(
+        "-a",
+        "--arch",
+        default="resnet18",
+        help="model architecture (default: resnet18)",
+    )
+    parser.add_argument(
+        "-s",
+        "--shape",
+        type=int,
+        nargs='+',
+        default="1 3 224 224",
+        help="input shape (default: 1 3 224 224)"
+    )
+    parser.add_argument(
+        "-o",
+        "--output",
+        type=str,
+        default="model.mge",
+        help="output filename"
+    )
+
+    args = parser.parse_args()
+
+    if 'resnet' in args.arch:
+        model = getattr(resnet_model, args.arch)(pretrained=True)
+    elif 'shufflenet' in args.arch:
+        model = getattr(snet_model, args.arch)(pretrained=True)
+    else:
+        print('unavailable arch {}'.format(args.arch))
+        sys.exit()
+    dump_static_graph(model, args.output, tuple(args.shape))
+
+
+if __name__ == "__main__":
+    main()
diff --git a/flow-python/examples/simple_det_classify/lite.py b/flow-python/examples/simple_det_classify/lite.py
new file mode 100644
index 0000000..d8ec894
--- /dev/null
+++ b/flow-python/examples/simple_det_classify/lite.py
@@ -0,0 +1,82 @@
+# MegFlow is Licensed under the Apache License, Version 2.0 (the "License")
+#
+# Copyright (c) 2019-2021 Megvii Inc. All rights reserved.
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT ARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+
+#!/usr/bin/env python
+# coding=utf-8
+
+import argparse
+import time
+import cv2
+import numpy as np
+import megenginelite as mgelite
+from loguru import logger
+
+
+class PredictorLite:
+    def __init__(
+        self,
+        path,
+        device="gpu",
+        device_id=0,
+    ):
+
+        if "gpu" in device.lower():
+            device_type = mgelite.LiteDeviceType.LITE_CUDA
+        else:
+            device_type = mgelite.LiteDeviceType.LITE_CPU
+
+        net_config = mgelite.LiteConfig(device_type=device_type)
+        ios = mgelite.LiteNetworkIO()
+        ios.add_input(mgelite.LiteIO("data", is_host=True))
+
+        net = mgelite.LiteNetwork(config=net_config, io=ios)
+        net.device_id = device_id
+        net.load(path)
+
+        self.net = net
+
+    def inference(self, img):
+        t0 = time.time()
+
+        img = cv2.resize(img, (224, 224))
+        # build input tensor
+        inp_data = self.net.get_io_tensor("data")
+        inp_data.set_data_by_share(img)
+
+        # forward
+        self.net.forward()
+        self.net.wait()
+
+        # postprocess
+        output_keys = self.net.get_all_output_name()
+        output = self.net.get_io_tensor(output_keys[0]).to_numpy()
+        logger.debug("resnet18 infer time: {:.4f}s".format(time.time() - t0))
+
+        return np.argmax(output[0])
+
+
+def make_parser():
+    parser = argparse.ArgumentParser("Classification Demo!")
+    parser.add_argument("--path",
+                        default="./test.png",
+                        help="path to images or video")
+    parser.add_argument("--model",
+                        default=None,
+                        type=str,
+                        help=".mge for eval")
+    return parser
+
+
+if __name__ == "__main__":
+    args = make_parser().parse_args()
+    predictor = PredictorLite(args.model)
+    image = cv2.imread(args.path)
+    if image is None:
+        logger.error(f"open {args.path} failed")
+    out = predictor.inference(image)
+    logger.info(f'{out}')
diff --git a/flow-python/examples/simple_det_classify/video_cpu.toml b/flow-python/examples/simple_det_classify/video_cpu.toml
new file mode 100644
index 0000000..f63a662
--- /dev/null
+++ b/flow-python/examples/simple_det_classify/video_cpu.toml
@@ -0,0 +1,45 @@
+main = "tutorial_02"
+
+[[nodes]]
+name = "det"
+ty = "Detect"
+model = "yolox-s"
+conf = 0.25
+nms = 0.45
+tsize = 640
+path = "models/simple_det_classify_models/yolox_s.mge"
+interval = 5
+visualize = 1
+device = "cpu"
+device_id = 0
+
+[[nodes]]
+name = "classify"
+ty = "Classify"
+path = "models/simple_det_classify_models/resnet18_preproc_inside.mge"
+device = "cpu"
+device_id = 0
+
+[[graphs]]
+name = "subgraph"
+inputs = [{ name = "inp", cap = 16, ports = ["det:inp"] }]
+outputs = [{ name = "out", cap = 16, ports = ["classify:out"] }]
+connections = [
+  { cap = 16, ports = ["det:out", "classify:inp"] },
+]
+
+[[graphs]]
+name = "tutorial_02"
+connections = [
+  { cap = 16, ports = ["source:out", "destination:inp"] },
+  { cap = 16, ports = ["source:inp", "destination:out"] }
+]
+
+    [[graphs.nodes]]
+    name = "source"
+    ty = "VideoServer"
+    port = 8085
+    
+    [[graphs.nodes]]
+    name = "destination"
+    ty = "subgraph"