code: def add(self, entity):
          
          characteristic = self.extract_traits(entity)
          if not characteristic.traits:
              return
  
          if characteristic.is_matching:
              self.add_match(entity, *characteristic.traits)
          else:
              self.add_mismatch(entity, *characteristic.traits)
docs: Add entity to index.
  
          :param object entity: single object to add to box's index