code: def remove_query_param(self, key, value=None):
          
          parse_result = self.query_params()
          if value is not None:
              index = parse_result[key].index(value)
              del parse_result[key][index]
          else:
              del parse_result[key]
          return URL._mutate(self, query=unicode_urlencode(parse_result, doseq=True))
docs: Remove a query param from a URL
  
          Set the value parameter if removing from a list.
  
          :param string key: The key to delete
          :param string value: The value of the param to delete (of more than one)