@classmethod<EOL><INDENT>def _allocate_ids(cls, size=None, max=None, parent=None, **ctx_options):<DEDENT>
return cls._allocate_ids_async(size=size, max=max, parent=parent,<EOL>**ctx_options).get_result()<EOL>
Allocates a range of key IDs for this model class.

        Args:
          size: Number of IDs to allocate. Either size or max can be specified,
            not both.
          max: Maximum ID to allocate. Either size or max can be specified,
            not both.
          parent: Parent key for which the IDs will be allocated.
          **ctx_options: Context options.

        Returns:
          A tuple with (start, end) for the allocated range, inclusive.