What is the role of handler.py in App Engine bulk upload/download?

I开发者_开发技巧 was reading the Google App Engine tutorial for bulk upload/download. Could somebody please tell me what is the role of the script : 'handler.py' that has to be specified in the app.yaml file ? The documentation does not specifically talk about the role of this script.

In the remote_api the handler.py is the script that will let locally executing python code access the remote app's datastore (after you've provided administrator authentication). Bulk loader needs it to push and pull data to/from your datastore.

I recommend using the builtins directive instead of adding that entry to your app.yaml