WHO                          UID  USER PID  COMM            WHAT                                                     WHY                                                         MODE 
Unattended Upgrades Shutdown 0    root 1274 unattended-upgr shutdown                                                 Stop ongoing upgrades or perform upgrades before shutdown   delay
GNOME Shell                  1000 imac 3054 gnome-shell     sleep                                                    GNOME needs to lock the screen                              delay
imac                         1000 imac 3191 gsd-power       handle-lid-switch                                        External monitor attached or configuration changed recently block
imac                         1000 imac 3190 gsd-media-keys  handle-power-key:handle-suspend-key:handle-hibernate-key GNOME handling keypresses                                   block

4 inhibitors listed.