code: def _add_missing_rows(self, indexes):
          
          new_indexes = [x for x in indexes if x not in self._index]
          for x in new_indexes:
              self._add_row(x)
docs: Given a list of indexes, find all the indexes that are not currently in the Series and make a new row for
          that index by appending to the Series. This does not maintain sorted order for the index.
  
          :param indexes: list of indexes
          :return: nothing