Bug

I would like to give some feedback about this... There seems to be a bug.

def checkio(number):
    num = int(number)
    answer = bin(num)
    return answer.count(1)

#These "asserts" using only for self-checking and not necessary for auto-testing
if __name__ == '__main__':
    assert checkio(4) == 1
    assert checkio(15) == 4
    assert checkio(1) == 1
    assert checkio(1022) == 9

From: https://checkio.org/mission/binary-count/solve/

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