docs: def parent(self):
          # type: () -> Any
          """Retrieve the parent of this `Part`.
  
          :return: the parent :class:`Part` of this part
          :raises APIError: if an Error occurs
  
          Example
          -------
  
          >>> part = project.part('Frame')
          >>> bike = part.parent()
  
          """
          if self.parent_id:
              return self._client.part(pk=self.parent_id, category=self.category)
          else:
              return None