code: def unregister(self, model):
          
          if model not in self._registry:
              raise KeyError("A permission handler class have not been "
                             "registered for '%s' yet" % model)
          # remove from registry
          del self._registry[model]
docs: Unregister a permission handler from the model
  
          Parameters
          ----------
          model : django model class
              A django model class
  
          Raises
          ------
          KeyError
              Raise when the model have not registered in registry yet.