getValidation method
Implementation
FieldValidation<T>? getValidation(String validationKey) {
for (var v in _children) {
if (v is FieldValidation<T> && v.validationKey == validationKey) return v;
if (v is Validator<T>) {
var result = v.getValidation(validationKey);
if (result != null) return result;
}
}
return null;
}