def METHOD_NAME():
    pj = PopJWT(
        "https://server.example.com", "https://client.example.org", sub="12345678"
    )
    pjwt = pj.pack_kid("some-key-id")
    s = pjwt.to_json()
    assert s
    de_pjwt = PJWT().from_json(s)
    assert _eq(de_pjwt.keys(), ["iss", "aud", "exp", "cnf", "sub", "iat"])
    assert list(de_pjwt["cnf"].keys()) == ["kid"]
    assert de_pjwt["cnf"]["kid"] == "some-key-id"