AttributeError: module 'typing' has no attribute 'UnionMeta'

[emmeowzing]

While running the following:

#! /usr/bin/env python3.6
# -*- coding: utf-8 -*-

from overloading import overload, overloaded, overloads
from unittest import TestCase, main
from typing import Union, Dict, Any, Iterable

class TestOverloading(TestCase):
    # Use overloading on functions with different types

    _add_types = Union[int, str, dict, set]

    @overload
    @staticmethod
    def add(x: int, y: int) -> int:
        return x + y

    @overload
    @staticmethod
    def add(x: str, y: str) -> str:
        return x + y

    @overload
    @staticmethod
    def add(x: Dict[Any, Any], y: Dict[Any, Any]) -> Dict[Any, Any]:
        return {**x, **y}

    @overload
    @staticmethod
    def add(x: set, y: set) -> set:
        return x | y

    @staticmethod
    def complete_add(x: _add_types, y: _add_types) -> _add_types:

        class TypeMismatchError(TypeError):
            pass

        if type(x) != type(y):
            raise TypeMismatchError(
                f'complete_add expected arguments of similar type, received {type(x)}, {type(y)}'
            )

        if (type(x) is int and type(y) is int):
            return x + y

        elif type(x) is str and type(y) is str:
            return x + y

        elif type(x) is dict and type(y) is dict:
            return {**x, **y}

        elif type(x) is set and type(y) is set:
            return x | y

        else:
            ts = ', '.join(_add_types.__args__)
            raise TypeError(
                f'complete_add expected arguments of type {ts} received {type(x)}'
            )

    def test1(self) -> None:

        self.assertEqual(self.add(1, 2), self.complete_add(1, 2))
        self.assertEqual(self.add('Brandon', ' Doyle'), self.complete_add('Brandon', ' Doyle'))
        self.assertEqual(self.add({1: 'one'}, {2: 'two'}), self.complete_add({1: 'one'}, {2: 'two'}))
        self.assertEqual(self.add({1}, {2}), self.complete_add({1}, {2}))

if __name__ == '__main__':
    main()

I get the following AttributeError:

Traceback (most recent call last):
  File "./test_overloading.py", line 9, in <module>
    class TestOverloading(TestCase):
  File "./test_overloading.py", line 21, in TestOverloading
    def add(x: str, y: str) -> str:
  File "/usr/local/lib/python3.6/site-packages/overloading-0.5.0-py3.6.egg/overloading.py", line 63, in overload
    return register(__registry[fname], func)
  File "/usr/local/lib/python3.6/site-packages/overloading-0.5.0-py3.6.egg/overloading.py", line 207, in register
    dup_sig = sig_cmp(signature, fninfo.signature)
  File "/usr/local/lib/python3.6/site-packages/overloading-0.5.0-py3.6.egg/overloading.py", line 669, in sig_cmp
    match = type_cmp(t1, t2)
  File "/usr/local/lib/python3.6/site-packages/overloading-0.5.0-py3.6.egg/overloading.py", line 702, in type_cmp
    if isinstance(t1, typing.UnionMeta) and isinstance(t2, typing.UnionMeta):
AttributeError: module 'typing' has no attribute 'UnionMeta'