308             wdg = widget(cls.vreg, cls, rschema, tschema, 'subject')

   308             wdg = widget(cls.vreg, cls, rschema, tschema, 'subject')

   309         else:

   309         else:

   310             tschema = rschema.subjects(cls.e_schema)[0]

   310             tschema = rschema.subjects(cls.e_schema)[0]

   311             wdg = widget(cls.vreg, tschema, rschema, cls, 'object')

   311             wdg = widget(cls.vreg, tschema, rschema, cls, 'object')

   312         return wdg

   312         return wdg

   313     def relations_by_category(self, categories=None, permission=None):

   314     def relations_by_category(self, categories=None, permission=None):

   314         if categories is not None:

   315         if categories is not None:

   315             if not isinstance(categories, (list, tuple, set, frozenset)):

   316             if not isinstance(categories, (list, tuple, set, frozenset)):

   316                 categories = (categories,)

   317                 categories = (categories,)

   317             if not isinstance(categories, (set, frozenset)):

   318             if not isinstance(categories, (set, frozenset)):