promql/value.go
func (r *Result) Vector() (Vector, error) {
	if r.Err != nil {
		return nil, r.Err
	}
	v, ok := r.Value.(Vector)
	if !ok {
		return nil, errors.New("query result is not a Vector")
	}
	return v, nil
}
func (r *Result) Vector() (Vector, error) {
	if r.Err != nil {
		return nil, r.Err
	}
	v, ok := r.Value.(Vector)
	if !ok {
		return nil, errors.New("query result is not a Vector")
	}
	return v, nil
}
// Vector returns a Vector if the result value is one. An error is returned if
// the result was an error or the result value is not a Vector.