code: def clear(self):
          
  
          # Create set of candidate_subclasses associated with each mention_subclass
          cand_subclasses = set()
          for mentions, tablename in [
              (_[1][0], _[1][1]) for _ in candidate_subclasses.values()
          ]:
              for mention in mentions:
                  if mention in self.mention_classes:
                      cand_subclasses.add(tablename)
  
          # First, clear all the Mentions. This will cascade and remove the
          # mention_subclasses and corresponding candidate_subclasses.
          for mention_class in self.mention_classes:
              logger.info(f"Clearing table: {mention_class.__tablename__}")
              self.session.query(Mention).filter_by(
                  type=mention_class.__tablename__
              ).delete(synchronize_session="fetch")
  
          # Next, clear the Candidates. This is done manually because we have
          # no cascading relationship from candidate_subclass to Candidate.
          for cand_subclass in cand_subclasses:
              logger.info(f"Cascading to clear table: {cand_subclass}")
              self.session.query(Candidate).filter_by(type=cand_subclass).delete(
                  synchronize_session="fetch"
              )
docs: Delete Mentions of each class in the extractor from the given split.