code: def search_value(self, xpath, default=None, single_value=True):
          
          matches = [match.value for match in parse(xpath).find(self.retval)]
          if len(matches) == 0:
              return default
          return matches[0] if single_value is True else matches
docs: Try to find a value in the result
  
          :param str xpath: a xpath filter see https://github.com/kennknowles/python-jsonpath-rw#jsonpath-syntax
          :param any default: default value if not found
          :param bool single_value: is the result is multivalued
          :return: the value found or None