docs: def find_permission(
          permissions, permission_type, object_id=None, namespace=None):
      '''Given a queryset of permissions, filters depending on the permission
      type, and optionally an object id and namespace.'''
      if object_id is not None:
          return permissions.filter(
              type=permission_type, object_id=object_id, namespace=namespace)
      return permissions.filter(type=permission_type)