make base internal (_base)

Author: AmandaBirmingham

metameq/config/standards.yml

@@ -119,7 +119,7 @@ host_body_site_skin_of_hand: &host_body_site_skin_of_hand
       function: "transform_format_field_as_int"
       overwrite_non_nans: true
 host_type_specific_metadata:
-  base:
+  _base:
     metadata_fields:
       sample_name:
         empty: false

metameq/tests/test_metadata_configurator/test_build_full_flat_config_dict.py

@@ -36,9 +36,9 @@ def test_build_full_flat_config_dict_no_inputs(self):
         hosts_dict = result[HOST_TYPE_SPECIFIC_METADATA_KEY]
         self.assertIsInstance(hosts_dict, dict)
 
-        # Should have "base" host type with sample_name metadata field
-        self.assertIn("base", hosts_dict)
-        base_host = hosts_dict["base"]
+        # Should have "_base" host type with sample_name metadata field
+        self.assertIn("_base", hosts_dict)
+        base_host = hosts_dict["_base"]
         self.assertIn(METADATA_FIELDS_KEY, base_host)
         self.assertIn("sample_name", base_host[METADATA_FIELDS_KEY])