code: def _wrap_callback_parse_stream_data(subscription, on_data, message):
      
      if (message.type == message.DATA and
              message.data.type == yamcs_pb2.STREAM_DATA):
          stream_data = getattr(message.data, 'streamData')
          on_data(StreamData(stream_data))
docs: Wraps an (optional) user callback to parse StreamData
      from a WebSocket data message