code: def filter_query(self, request, query, view):
          
  
          if not request.params:
              return query
  
          querystring_params = self.parse_query_string(request.params)
          query, filter_list = self.build_filter_list(querystring_params, query, view)
  
          return self.apply_filter(query, filter_list)
docs: You may want to override this method if you want to add custom filtering to an ViewSet while still
          utilizing the feature of the ``AttributeFilter`` implementation.
  
          :param request: The pyramid ``Request`` instance.
          :param query: The SQLAlchemy ``Query`` instance.
          :param view: An instance of the view class that the filter has been applied to.
          :return: The filtered query.