def METHOD_NAME(filepath, data):
    # Untweaked key begins as half-advanced "0xBABE"
    h = two_rounds(pack(b"<QQQQQQQQ", 0xBABE, 0, 0, 0, 0, 0, 0, 0))
    h = mix_in_filepath(filepath, h)
    # Add the tweaked key and its advancement, then advance by four round pairs.
    key = quad_rounds(add_qwords(h, quad_rounds(h)))
    return chacha_rest(data, key)