def is_mod10_valid(number):
        """
        Returns whether or not the card's number validates against the mod10
        algorithm (Luhn algorithm), automatically returning False on an empty
        value.
        """
        # Check for empty string
        if not number:
            return False

        # Run mod10 on the number
        dub, tot = 0, 0
        for i in range(len(number) - 1, -1, -1):
            for c in str((dub + 1) * int(number[i])):
                tot += int(c)
            dub = (dub + 1) % 2

        return (tot % 10) == 0