The place to learn more about Qtile is
http://docs.qtile.org/en/latest/
We found a widget we can add to our menu bar called NetGraph.
http://docs.qtile.org/en/latest/manual/ref/widgets.html#netgraph
We will make it together.
Start with a copy/paste and start changing the lines and compare between widgets what the writing syntax is.
We check on qtile.org what variables I can use in the widget.
Change one thing and reload qtile to check if it crashes already.
Then you know what to change.
Follow the video to see the development workflow.