code: def get_permission_required(cls):
          
          if cls.permission_required is None:
              raise ImproperlyConfigured(
                  "{0} is missing the permission_required attribute. "
                  "Define {0}.permission_required, or override "
                  "{0}.get_permission_required().".format(cls.__name__)
              )
          if isinstance(cls.permission_required, six.string_types):
              if cls.permission_required != "":
                  perms = (cls.permission_required,)
              else:
                  perms = ()
          else:
              perms = cls.permission_required
  
          return perms
docs: Get permission required property.
          Must return an iterable.