What's the game and caller PIDs ordering in DBus API?

[gasinvein]

Hello. I was was studying GameMode DBus APIs and got myself confused. What is order of game and caller PID arguments in *ByPID methods?

The dbus call handler method_register_game_by_pid() suggests it's (caller,game): https://github.com/FeralInteractive/gamemode/blob/4000a32584a9eb3964813b8fdbb279be7beb24cc/daemon/gamemode-dbus.c#L146-L152

But most of rest of the code suggests it's (game,caller), e.g. in gamemode_request() in client, as far as I understand, client sends the target pid first: https://github.com/FeralInteractive/gamemode/blob/4000a32584a9eb3964813b8fdbb279be7beb24cc/lib/client_impl.c#L307-L315

Also the xdg-desktop-portal implementation has named arguments (target,requester), what suggests (game,caller), too.

So, which one is correct?