code: func funcQuantileOverTime(vals []Value, args Expressions, enh *EvalNodeHelper) Vector {
  	q := vals[0].(Vector)[0].V
  	mat := vals[1].(Matrix)
  
  	for _, el := range mat {
  		if len(el.Points) == 0 {
  			continue
  		}
  
  		values := make(vectorByValueHeap, 0, len(el.Points))
  		for _, v := range el.Points {
  			values = append(values, Sample{Point: Point{V: v.V}})
  		}
  		enh.out = append(enh.out, Sample{
  			Point: Point{V: quantile(q, values)},
  		})
  	}
  	return enh.out
  }
docs: // === quantile_over_time(Matrix ValueTypeMatrix) Vector ===