promql/functions.go
func funcDelta(vals []Value, args Expressions, enh *EvalNodeHelper) Vector {
	return extrapolatedRate(vals, args, enh, false, false)
}
func funcDelta(vals []Value, args Expressions, enh *EvalNodeHelper) Vector {
	return extrapolatedRate(vals, args, enh, false, false)
}
// === delta(Matrix ValueTypeMatrix) Vector ===