human
I wrote the below code

    def window(a, n=100):
        if (n > 0):
            for i in xrange(max(((len(a) - n) + 1), 1)):
                (yield a[i:(i + n)])
    s = string.lower().split()
    s = [w.strip(punctuation) for w in s]
    return mean((((1.0 * len(set(x))) / max(len(x), 1)) for x in window(s, n)))

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

def type_token_ratio(string, n=100, punctuation=PUNCTUATION):