<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def save_to_store(self):
 """Save index to store. :raise AttributeError: If no datastore is defined """

        if not self._store:
            raise AttributeError('No datastore defined!')
        saved_data = self.save_to_data(in_place=True)
        data = Serializer.serialize(saved_data)
        self._store.store_blob(data, 'all_keys_with_undefined')