def METHOD_NAME(self):
    token_count = [0]
    class CustomTransformer(TreeForestTransformer):
        def __default_token__(self, node):
            token_count[0] += 1
            assert isinstance(node, Token)
    tree = CustomTransformer(resolve_ambiguity=True).transform(self.forest)
    self.assertEqual(token_count[0], 4)