code: def related_model(self):
          
          relationship_field = self.name
  
          if relationship_field not in get_relationships(self.schema):
              raise InvalidFilters("{} has no relationship attribute {}".format(self.schema.__name__, relationship_field))
  
          return getattr(self.model, get_model_field(self.schema, relationship_field)).property.mapper.class_
docs: Get the related model of a relationship field
  
          :return DeclarativeMeta: the related model