promql/functions.go
func funcSumOverTime(vals []Value, args Expressions, enh *EvalNodeHelper) Vector {
	return aggrOverTime(vals, enh, func(values []Point) float64 {
		var sum float64
		for _, v := range values {
			sum += v.V
		}
		return sum
	})
}
func funcSumOverTime(vals []Value, args Expressions, enh *EvalNodeHelper) Vector {
	return aggrOverTime(vals, enh, func(values []Point) float64 {
		var sum float64
		for _, v := range values {
			sum += v.V
		}
		return sum
	})
}
// === sum_over_time(Matrix ValueTypeMatrix) Vector ===