help with keybinding - open function description

Hi, could someone please help me with this: what is the keybinding to open those pop-up windows which show the function description? See my screenshot. In other editors it's sometimes called "code lense".

I've looked everywhere and I simply cannot find it (if I only knew how the action is called in the settings file...). I'm using a tiling window manager, so I don't want to use the mouse every time. Thanks.