typehints with_output_types annotation doesn't work for stateful DoFn

The output types typehints seem to be ignored when using a stateful DoFn, but the same typehint works perfectly when used without state. This issue prevents a custom Coder from being used because Beam will default to one of the FastCoders (I believe Pickle).

Example code:

@typehints.with_output_types(Message)
class StatefulDoFn(DoFn):

    COUNTER_STATE = BagStateSpec('counter', VarIntCoder())
    def process(self, element, counter=DoFn.StateParam(COUNTER_STATE)):
      (key, messages) = element
      newMessage = Message()
      return [newMessage]

The example code is just defining a stateful DoFn for python. The used runner is the Flink 1.6.4 portable runner.

Finally, overriding infer_output_type to return a typehints.List[Message] solves the issue.

Looking at the code, it seems to me that in https://github.com/apache/beam/blob/v2.13.0/sdks/python/apache_beam/pipeline.py#L643 we do not take the typehints into account.