Model class actually have to_xml() function but this xml schema not customizable and entity based. You can export your model as xml with bit of code:
This functionality is good for data exporting operations:
class TestModule(webapp.RequestHandler):
def get(self):
props = AuditLog().properties()
data = "\n"
for prop in props:
data = data + " <{0}>{{{{i.{0}}}}}</{0}>\n".format(prop)
data = data + ""
self.response.out.write(data)