func (a *NestedAggregation) Meta(metaData map[string]interface{}) *NestedAggregation {
	a.meta = metaData
	return a
}
Meta sets the meta data to be included in the aggregation response.
package elastic
type NestedAggregation struct {
	path            string
	subAggregations map[string]Aggregation
	meta            map[string]interface{}
}
func NewNestedAggregation() *NestedAggregation {
	return &NestedAggregation{
		subAggregations: make(map[string]Aggregation),
	}
}
func (a *NestedAggregation) SubAggregation(name string, subAggregation Aggregation) *NestedAggregation {
	a.subAggregations[name] = subAggregation
	return a
}