docs: def next(self):
          """Advance the cursor."""
          if self.__empty:
              raise StopIteration
          if len(self.__data) or self._refresh():
              if self.__manipulate:
                  _db = self.__collection.database
                  return _db._fix_outgoing(self.__data.popleft(),
                                           self.__collection)
              else:
                  return self.__data.popleft()
          else:
              raise StopIteration