code: def _extract_value_from_storage(self, string):
          
          parts = string.split(self.separator)
          pk = parts.pop()
          return self.separator.join(parts), pk
docs: Taking a string that was a member of the zset, extract the value and pk
  
          Parameters
          ----------
          string: str
              The member extracted from the sorted set
  
          Returns
          -------
          tuple
              Tuple with the value and the pk, extracted from the string