human
Here's a good function header given the following:
I wrote the below code

    arrayExpr = Forward()
    def countFieldParseAction(s, l, t):
        n = t[0]
        (arrayExpr << ((n and Group(And(([expr] * n)))) or Group(empty)))
        return []
    if (intExpr is None):
        intExpr = Word(nums).setParseAction((lambda t: int(t[0])))
    else:
        intExpr = intExpr.copy()
    intExpr.setName('arrayLen')
    intExpr.addParseAction(countFieldParseAction, callDuringTry=True)
    return (intExpr + arrayExpr).setName((('(len)    ' + _ustr(expr)) + '...'))

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

def countedArray(expr, intExpr=None):