HowTo: Detect Laptop waking up from suspend from Emacs

[raman]

Background:

I run Emacs as my primary environment -- ie I do everything in Emacs
on Linux.

So when I open my laptop lid, my laptop wakes up from suspend and
Emacs is where I left off.

I'd like to set things up so emacs runs a set of actions when the
laptop comes back from suspend -- typically, say 5 seconds after
wake-up. Here, all actions are emacs functions.

So Q:

>From Emacs --- perhaps an idle-timer, how do I detect when the laptop
returns from suspend?
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