Programatically list all feature classes used by a published map service?

Hi all,

I'm trying to figure out how to list all features used by a published map service. So "xyz" is published on a map server, I'm wanting to programatically list all the feature classes (in a gdb) that share a relation with "xyz". Something using arcpy would be nice, but I'm not finding anything! Any help is appreciated.

Thanks

Jesse