1
2def test(**kw):
3    """
4    >>> d = {1 : 2}
5    >>> test(**d)       # doctest: +ELLIPSIS
6    Traceback (most recent call last):
7    TypeError: ...keywords must be strings
8    >>> d
9    {1: 2}
10    >>> d = {}
11    >>> test(**d)
12    {'arg': 3}
13    >>> d
14    {}
15    >>> d = {'arg' : 2}
16    >>> test(**d)
17    {'arg': 3}
18    >>> d
19    {'arg': 2}
20    """
21    kw['arg'] = 3
22    return kw
23