code: def prev_listing(self, limit=None):
          
          if self.before:
              return self._reddit._limit_get(self._path, eparams={'before': self.before}, limit=limit or self._limit)
          else:
              raise NoMoreError('no previous items')
docs: GETs previous :class:`Listing` directed to by this :class:`Listing`.  Returns :class:`Listing` object.
          
          :param limit: max number of entries to get