code: def _check_params(self,params):
          
          overridden_object_params = list(self._overridden.param)
          for item in params:
              if item not in overridden_object_params:
                  self.param.warning("'%s' will be ignored (not a Parameter).",item)
docs: Print a warning if params contains something that is not a
          Parameter of the overridden object.