OpenLayers 2.x is not under active development any more. Go to http://openlayers.org/en/latest/doc/ to view the latest OpenLayers 3.x docs.
In this tutorial we would create a TG2 app and use tg.ext.geo extension to
mount the TileCache WSGI App. We would also modify the template code for index
method to create an OpenLayers Map that would render the tiles.