def METHOD_NAME(string):
    num = string[0] if isinstance(string[0], int) else ord(string[0])
    if not string.startswith(b'\x03'):
        raise UnexpectedDER("wanted bitstring (0x03), got 0x%02x" % num)
    length, llen = read_length(string[1:])
    body = string[1+llen:1+llen+length]
    rest = string[1+llen+length:]
    return body, rest