Breaking out of the Google App Engine Python lock-in?

Are there any guidelines to writing Google App Engine Python code that would work without Google's infrastructure on other platforms?

Is there any known attempt to create an open source framework which can run applications designed for Google App Engine on other platforms?

Edit:

To clarify, the question really is:

If I develop an application on Google App Engine now, will I be able to migrate to another platform later, or is it a lock in?