pythonpath_contrib extension point

In my plugin I am contributing to the PythonPath. I noticed the documentation says that if the contribution changes, then the user has to go in to the dialog and press the “Force internal restore” button. I thought I could maybe do better than that programmatically, so when my contribution changes I get all the PythonNatures in the workspace and call PythonNature.rebuildPath() on them. This seems to work well, with one exception—the auto-completion cache.

So, for example, say that I am initially contributing nothing. In the editor, auto-completion suggests nothing from my code. Now, I make a change to start contributing a directory, and when I do that I rebuild paths as described above. Now my contributions are suggested by auto-completion. Now, suppose I remove my contribution and rebuild paths again, my contributions are still suggested. I believe it is because of the completion cache, because if I close the project and re-open, my contributions are no longer suggested again.

Is it safe for me to just clear that the completion cache directly, or should PythonNature.rebuildPath() be changed to clear it, or am I wrong altogether?