$ gdbus call --system --dest org.freedesktop.login1 --object-path /org/freedesktop/login1 --method org.freedesktop.login1.Manager.CanSuspend
(and same with Hibernate)
$ gdbus call --system --dest org.freedesktop .login1 --object-path /org/freedeskto p/login1 --method org.freedesktop .login1. Manager. CanSuspend
(and same with Hibernate)