code: def remove(self, entity):
          
          empty_traits = set()
          self.mismatch_unknown.discard(entity)
          for trait, entities in self.index.items():
              entities.discard(entity)
              if not entities:
                  empty_traits.add(trait)
  
          for empty_trait in empty_traits:
              del self.index[empty_trait]
docs: Remove entity from the MatchBox.
  
          :param object entity: