private IObjectValidator GetValidator()
{
var builder = new ValidationBuilder <InnerValidatableObjectAndCollectionViewModel>();
builder.RuleFor(vm => vm.InnerObjectValue)
.NotNull()
.ModelIsValid();
builder.RuleForCollection(vm => vm.InnerObjectsCollection)
.NotNull()
.Count(3, 5)
.CollectionElementsAreValid(i => i.Validator?.IsValid != false);
return(builder.Build(this));
}