code: def _extract_relations(self, attribute: str) -> Tuple[List[str], str]:
          
          splitted = attribute.split(self._attr_sep)
          return (splitted[:-1], splitted[-1])
docs: Split and return the list of relation(s) and the attribute.
  
          :param attribute:
          :type attribute: str
  
          :return: A tuple where the first element is the list of related
              entities and the second is the attribute.
          :rtype: Tuple[List[str], str]