code: def deleted(self, key, value):
      
      def _is_deleted(value):
          return force_single_element(value.get('c', '')).upper() == 'DELETED'
  
      def _is_stub(value):
          return not (force_single_element(value.get('a', '')).upper() == 'USEFUL')
  
      deleted = self.get('deleted')
      stub = self.get('stub')
  
      for value in force_list(value):
          deleted = not deleted and _is_deleted(value)
          stub = not stub and _is_stub(value)
  
      self['stub'] = stub
      return deleted
docs: Populate the ``deleted`` key.
  
      Also populates the ``stub`` key through side effects.