def METHOD_NAME(self):
    """
    This is a situation that should never happen.
    But we are creating it artificially.
    """
    t1 = {1: 1}
    t2 = {1: 2}
    child_t1 = {}
    child_t2 = {}
    up = DiffLevel(t1, t2)
    down = up.down = DiffLevel(child_t1, child_t2)
    path = down.path()
    assert path == 'root'
    assert down.path(output_format='list') == []