code: 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
  	})
  }
docs: // === sum_over_time(Matrix ValueTypeMatrix) Vector ===