code: def _allocate_ids(cls, size=None, max=None, parent=None, **ctx_options):
      
      return cls._allocate_ids_async(size=size, max=max, parent=parent,
                                     **ctx_options).get_result()
docs: 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.