fix lint

Signed-off-by: Jeffrey Kinard <[email protected]>

sdks/python/apache_beam/yaml/yaml_ml.py

@@ -155,7 +155,7 @@ def __init__(
     so that input data can be sent using an API request, and inferences can be
     received as a response.
 
-    This Model Handler also required a `preprocess` function to be defined.
+    This Model Handler also requires a `preprocess` function to be defined.
     Preprocessing and Postprocessing are described in more detail in the
     RunInference docs:
     https://beam.apache.org/releases/yamldoc/current/#runinference
@@ -249,6 +249,11 @@ def inference_output_type(self):
                                           ('model_id', Optional[str])])
 
 
+def get_user_schema_fields(user_type):
+  return [(name, type(typ) if not isinstance(typ, type) else typ)
+          for (name, typ) in user_type._fields] if user_type else []
+
+
 @beam.ptransform.ptransform_fn
 def run_inference(
     pcoll,
@@ -434,18 +439,17 @@ def fn(x: PredictionResult):
   if missing_params:
     raise ValueError(f'Missing parameters in model_handler: {missing_params}')
   typ = model_handler['type']
-  model_handler_provider = ModelHandlerProvider.handler_types.get(typ, None)
-  if model_handler_provider and issubclass(model_handler_provider,
-                                           type(ModelHandlerProvider)):
-    model_handler_provider.validate(model_handler['config'])
-  else:
+  model_handler_provider_type = ModelHandlerProvider.handler_types.get(
+      typ, None)
+  if not model_handler_provider_type:
     raise NotImplementedError(f'Unknown model handler type: {typ}.')
 
   model_handler_provider = ModelHandlerProvider.create_handler(model_handler)
+  model_handler_provider.validate(model_handler['config'])
   user_type = RowTypeConstraint.from_user_type(pcoll.element_type.user_type)
   schema = RowTypeConstraint.from_fields(
-      list(user_type._fields if user_type else []) +
-      [(inference_tag, model_handler_provider.inference_output_type())])
+      get_user_schema_fields(user_type) +
+      [(str(inference_tag), model_handler_provider.inference_output_type())])
 
   return (
       pcoll | RunInference(