def __new__(cls, s, bits):
    """Create a bit string instance,
        
        `s`,
            Bytes representing the binary part of bit-string
        `bits`,
            count value from 0 to 8 representing valid number bits in the last
            byte of `s`.
        """
    obj = super().__new__(cls, s)
    obj.bits = bits
    obj.s = s
    return obj
