Google App Engine - Tracking which indexes are used

I have a App Engine/Python/Django application which has grown and been modified over the past year and currently has 175 indexes. The problem is that I have not been thourough in cleaning up/removing indexes that are no longer needed. Now, I am not sure which indexes are active and which are essentially dead, but I am guessing that about 20% of the idexes are useless.I have a App Engine/Python/Django application w