lessThan method
Checks if the object is a number and is less than another value
Implementation
AbstractRuleBuilder lessThan(int min, {String? message}) {
return must(
(dynamic dyn) => dyn is num && dyn < min,
message != null
? message
: useKeyAsElementName
? "$key must be less than $min"
: "Number must be less than $min",
code: "notLessThen");
}