code: def read_data_transition(self, length, whence=None,
                               skip=False, stream_event=ION_STREAM_INCOMPLETE_EVENT):
          
          if whence is None:
              whence = self.whence
  
          return Transition(
              None, _read_data_handler(length, whence, self, skip, stream_event)
          )
docs: Returns an immediate event_transition to read a specified number of bytes.