def METHOD_NAME(config: dict) -> Set[str]:
    # This is a bit of a hack, but expandvars does a bunch of escaping
    # and other logic that we don't want to duplicate here.
    with unittest.mock.patch("expandvars.getenv") as mock_getenv:
        mock_getenv.return_value = "mocked_value"
        resolve_env_variables(config)
    calls = mock_getenv.mock_calls
    return set([call[1][0] for call in calls])