version resilient model could not handle type alias correctly

[tadelesh]

For example,

MyNamedUnion = Union["UnionModel1", "UnionModel2"]

class ModelWithNamedUnionProperty(Model):
    named_union: "MyNamedUnion" = rest_field(name="namedUnion")

class UnionModel1(Model):
    prop1: int = rest_field()

class UnionModel2(Model):
    prop2: int = rest_field()

test = ModelWithNamedUnionProperty({"namedUnion": {"prop1": 1}})

currently, test.named_union is a raw dict, the MyNamedUnion typing is not handled correctly.