code: def _check_time_fn(self, time_instance=False):
          
          if time_instance and not isinstance(self.time_fn, param.Time):
              raise AssertionError("%s requires a Time object"
                                   % self.__class__.__name__)
  
          if self.time_dependent:
              global_timefn = self.time_fn is param.Dynamic.time_fn
              if global_timefn and not param.Dynamic.time_dependent:
                  raise AssertionError("Cannot use Dynamic.time_fn as"
                                       " parameters are ignoring time.")
docs: If time_fn is the global time function supplied by
          param.Dynamic.time_fn, make sure Dynamic parameters are using
          this time function to control their behaviour.
  
          If time_instance is True, time_fn must be a param.Time instance.