code: func (a *BucketSortAggregation) Meta(meta map[string]interface{}) *BucketSortAggregation {
  	a.meta = meta
  	return a
  }
docs: // Meta sets the meta data in the aggregation.
  // Although metadata is supported for this aggregation by Elasticsearch, it's important to
  // note that there's no use to it because this aggregation does not include new data in the
  // response. It merely reorders parent buckets.