code: def process_item(self, datum, keys=None):
          
          response = self.interact(datum)
          if keys is not None:
              response['keys'] = keys
          if 'task' not in response and self.task is not None:
              response['task'] = self.task
          return response
docs: Send *datum* to ACE and return the response with context.
  
          The *keys* parameter can be used to track item identifiers
          through an ACE interaction. If the `task` member is set on
          the AceProcess instance (or one of its subclasses), it is
          kept in the response as well.
          Args:
              datum (str): the input sentence or MRS
              keys (dict): a mapping of item identifier names and values
          Returns:
              :class:`~delphin.interfaces.ParseResponse`