human
I wrote the below code

    def censor(ch):
        if (((ch >= 'A') and (ch <= 'z')) or ((ch >= '0') and (ch <= '9'))):
            return ch
        return '*'
    return ''.join((censor(ch) for ch in s))

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

def censor_non_alphanum(s):