Document description of revert_url

Author: macro1

simple_history/models.py

@@ -162,6 +162,7 @@ def get_extra_fields(self, model, fields):
 
         @models.permalink
         def revert_url(self):
+            """URL for this change in the default admin site."""
             opts = model._meta
             try:
                 app_label, model_name = opts.app_label, opts.module_name