equal method
Checks if the object is equal to another one
Implementation
AbstractRuleBuilder equal(dynamic obj,
{dynamic objNameOrValue, String? message}) {
return must(
(dynamic dyn) => dyn == obj,
message != null
? message
: useKeyAsElementName
? "$key must be equal $objNameOrValue"
: "Value must be equal $objNameOrValue",
code: "notEqual");
}