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