update your web services to use elgg_ws_expose_function()

After upgrading from elgg 1.8 to elgg 1.9 and enabling the Web services plugin I've been getting the following message in my admin panel. My server is vps running ubuntu 12.04.

The web services are now a plugin in Elgg 1.9. You must enable this plugin and update your web services to use elgg_ws_expose_function().

I couldn't find a solution in the elgg documentation linked here! Any ideas on how I can update my web services to use elgg_ws_expose_function()?