obj.hide_viewport works for me, hiding and unhiding.
Note that the outliner does not hide objects using that prop, and neither does Blender’s object.hide_view_set() operator (H, SHIFT-H, ALT-H). They hide on the view layer level, which we can’t do via the API right now.
Also note, that there is this bug right now.
I assume hiding on the object level is going to be phased out and replaced with hiding on the view layer level, but I’m not sure.