def METHOD_NAME(key, d):
    """
    Return element of the dict to do the insertion on. If it is foo.1.bar, it
    will return d["foo"][1]. If it is only foo, it will return d directly.
    """
    path = key.split('.')[:-1]
    tmp_d = d
    for p in path:
        if isinstance(tmp_d, (list, tuple)):
            tmp_d = tmp_d[int(p)]
        else:
            tmp_d = tmp_d[p]
    return tmp_d