def METHOD_NAME(
    *,
    format=1,
    lowest_compatible=4,
    net_magic="regtest",
    bucket_key=1,
    len_new=None,
    len_tried=None,
    mock_checksum=None,
):
    new = []
    tried = []
    INCOMPATIBILITY_BASE = 32
    r = MAGIC_BYTES[net_magic]
    r += struct.pack("B", format)
    r += struct.pack("B", INCOMPATIBILITY_BASE + lowest_compatible)
    r += ser_uint256(bucket_key)
    r += struct.pack("<i", len_new or len(new))
    r += struct.pack("<i", len_tried or len(tried))
    ADDRMAN_NEW_BUCKET_COUNT = 1 << 10
    r += struct.pack("<i", ADDRMAN_NEW_BUCKET_COUNT ^ (1 << 30))
    for _ in range(ADDRMAN_NEW_BUCKET_COUNT):
        r += struct.pack("<i", 0)
    checksum = hash256(r)
    r += mock_checksum or checksum
    return r