remove unneeded code from workflow_by_code.ipynb && fix analysis_model_performance (#740)

Author: zhupr

examples/workflow_by_code.ipynb

@@ -62,12 +62,6 @@
     "import qlib\n",
     "import pandas as pd\n",
     "from qlib.config import REG_CN\n",
-    "from qlib.contrib.model.gbdt import LGBModel\n",
-    "from qlib.contrib.data.handler import Alpha158\n",
-    "from qlib.contrib.evaluate import (\n",
-    "    backtest as normal_backtest,\n",
-    "    risk_analysis,\n",
-    ")\n",
     "from qlib.utils import exists_qlib_data, init_instance_by_config\n",
     "from qlib.workflow import R\n",
     "from qlib.workflow.record_temp import SignalRecord, PortAnaRecord\n",

qlib/contrib/report/analysis_model/analysis_model_performance.py

@@ -57,7 +57,7 @@ def _group_return(pred_label: pd.DataFrame = None, reverse: bool = False, N: int
     ).figure
 
     t_df = t_df.loc[:, ["long-short", "long-average"]]
-    _bin_size = ((t_df.max() - t_df.min()) / 20).min()
+    _bin_size = float(((t_df.max() - t_df.min()) / 20).min())
     group_hist_figure = SubplotsGraph(
         t_df,
         kind_map=dict(kind="DistplotGraph", kwargs=dict(bin_size=_bin_size)),