code: def update_field(uid, post_id=None, tag_id=None, par_id=None):
          '''
          Update the field of post2tag.
          '''
          if post_id:
              entry = TabPost2Tag.update(
                  post_id=post_id
              ).where(TabPost2Tag.uid == uid)
              entry.execute()
  
          if tag_id:
              entry2 = TabPost2Tag.update(
                  par_id=tag_id[:2] + '00',
                  tag_id=tag_id,
              ).where(TabPost2Tag.uid == uid)
              entry2.execute()
          if par_id:
              entry2 = TabPost2Tag.update(
                  par_id=par_id
              ).where(TabPost2Tag.uid == uid)
              entry2.execute(f update_field(uid, post_id=None, tag_id=None, par_id=None):
          '''
          Update the field of post2tag.
          '''
          if post_id:
              entry = TabPost2Tag.update(
                  post_id=post_id
              ).where(TabPost2Tag.uid == uid)
              entry.execute()
  
          if tag_id:
              entry2 = TabPost2Tag.update(
                  par_id=tag_id[:2] + '00',
                  tag_id=tag_id,
              ).where(TabPost2Tag.uid == uid)
              entry2.execute()
          if par_id:
              entry2 = TabPost2Tag.update(
                  par_id=par_id
              ).where(TabPost2Tag.uid == uid)
              entry2.execute()
docs: Update the field of post2tag.