func (a *BucketSortAggregation) Meta(meta map[string]interface{}) *BucketSortAggregation {
	a.meta = meta
	return a
}
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.
package elastic
type BucketSortAggregation struct {
	sorters   []Sorter
	from      int
	size      int
	gapPolicy string
	meta map[string]interface{}
}
func NewBucketSortAggregation() *BucketSortAggregation {
	return &BucketSortAggregation{
		size: -1,
	}
}
func (a *BucketSortAggregation) Sort(field string, ascending bool) *BucketSortAggregation {
	a.sorters = append(a.sorters, SortInfo{Field: field, Ascending: ascending})
	return a
}
func (a *BucketSortAggregation) SortWithInfo(info SortInfo) *BucketSortAggregation {
	a.sorters = append(a.sorters, info)
	return a
}
func (a *BucketSortAggregation) From(from int) *BucketSortAggregation {
	a.from = from
	return a
}
func (a *BucketSortAggregation) Size(size int) *BucketSortAggregation {
	a.size = size
	return a
}
func (a *BucketSortAggregation) GapPolicy(gapPolicy string) *BucketSortAggregation {
	a.gapPolicy = gapPolicy
	return a
}
func (a *BucketSortAggregation) GapInsertZeros() *BucketSortAggregation {
	a.gapPolicy = "insert_zeros"
	return a
}
func (a *BucketSortAggregation) GapSkip() *BucketSortAggregation {
	a.gapPolicy = "skip"
	return a
}