range.go
func (r *Range) Check(value float64) bool {
	// Ranges are treated as a closed interval.
	if r.Start <= value && value <= r.End {
		return r.AlertOnInside
	}
	return !r.AlertOnInside
}
func (r *Range) Check(value float64) bool {
	// Ranges are treated as a closed interval.
	if r.Start <= value && value <= r.End {
		return r.AlertOnInside
	}
	return !r.AlertOnInside
}
// Check returns true if an alert should be raised based on the range (if the
// value is outside the range for normal semantics, or if the value is
// inside the range for inverted semantics ('@-semantics')).