human
I wrote the below code

    assert (len(tokens) == 1)
    assert (tokens[0][0] == u'@')
    macro_name = tokens[0][1:]
    def macro_use(n, m=None, l=None):
        if ((m is None) or (macro_name not in m)):
            raise TgrepException(u'macro    {0}    not    defined'.format(macro_name))
        return m[macro_name](n, m, l)
    return macro_use

What's a good function header?
assistant
#Here's a good function header.

def _tgrep_macro_use_action(_s, _l, tokens):