code: def build_permission_name(model_class, prefix):
      
      model_name = model_class._meta.object_name.lower()
      app_label = model_class._meta.app_label
      action_name = prefix
      perm = '%s.%s_%s' % (app_label, action_name, model_name)
      return perm
docs: Build permission name for model_class (like 'app.add_model').