Giving perfect output but...

I would like to give some feedback about ...

From: http://www.checkio.org/mission/fizz-buzz/solve/

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Hello, I got perfect output i.e for checkio(15) code printed "Fizz Bizz" but yet it shows incorrect output for checkio 15!!

MY CODE:

def checkio(number):
    if number % 3 == 0 and number % 5 == 0:
        print "Fizz Buzz"
    elif number % 3 == 0:
        print "Fizz"
    elif number % 5 == 0:
        print "Buzz"
    else:
        print str(number)
    return str(number)


checkio(15)