def METHOD_NAME(self):
    dct = dict(a=dict(a1=1, a2=2), b=dict(b1=dict(b11=11, b12=dict(b121=121))))
    self.assertDictEqual(
        {
            "a1": [("a", "a1")],
            "a2": [("a", "a2")],
            "b11": [("b", "b1", "b11")],
            "b121": [("b", "b1", "b12", "b121")],
        },
        nested_dict_crawler(dct),
    )