query.go
func (q *Query) Filter(rule string) *Query {
	q.headers = append(q.headers, "Filter: "+rule)
	return q
}
func (q *Query) Filter(rule string) *Query {
	q.headers = append(q.headers, "Filter: "+rule)
	return q
}
func ( q * Query ) Filter ( rule string ) * Query { q . headers = append ( q . headers , " " + rule ) return q }
// Filter appends a new filter to the query.
Filter appends a new filter to the query .