def _append_meta(self, id_, meta_data):
    id_ = str(id_)
    if (id_ not in self.meta_dict):
        self.meta_dict[id_] = self._default_factory()
    self.meta_dict[id_]['meta_data'].append(meta_data)
def _append_meta(self, id_, meta_data):
    id_ = str(id_)
    if (id_ not in self.meta_dict):
        self.meta_dict[id_] = self._default_factory()
    self.meta_dict[id_]['meta_data'].append(meta_data)