code: func (ng *Engine) NewInstantQuery(q storage.Queryable, qs string, ts time.Time) (Query, error) {
  	expr, err := ParseExpr(qs)
  	if err != nil {
  		return nil, err
  	}
  	qry := ng.newQuery(q, expr, ts, ts, 0)
  	qry.q = qs
  
  	return qry, nil
  }
docs: // NewInstantQuery returns an evaluation query for the given expression at the given time.