title: What is timeout_id in GTK for?
body: <p>I'm reading through the official PyGObject tutorial, and I found this (unexplained) line in one of the examples:</p>
  
  <pre><code>self.timeout_id = None
  </code></pre>
  
  <p>(it was within an <code>__init__</code> function of a <code>Gtk.Window</code>-descendant class; the whole listing is <a href="http://python-gtk-3-tutorial.readthedocs.org/en/latest/entry.html#example" rel="nofollow">here</a>).  I couldn't google it; what is it for?</p>