overriding iteration_log and epoch_log in StatsHandler

[wyli]

Currently, they are booleans but we could extend them to Union[bool, Callable] where if arg is callable then it could be used for event filtering:

    def attach(self, engine):


         if self.iteration_log and not engine.has_event_handler(self.iteration_completed, Events.ITERATION_COMPLETED):
             event_filter = self.iteration_log if callable(self.iteration_log) else None
             engine.add_event_handler(
                 Events.ITERATION_COMPLETED(event_filter=event_filter), self.iteration_completed
             ) 
         if self.epoch_log and not engine.has_event_handler(self.epoch_completed, Events.EPOCH_COMPLETED):
             event_filter = self.epoch_log if callable(self.epoch_log) else None
             engine.add_event_handler(
                 Events.EPOCH_COMPLETED(event_filter=event_filter), self.epoch_completed
             ) 

Originally posted by @vfdev-5 in #5958 (reply in thread)

[Nic-Ma]

Hi @vfdev-5 ,

Would you like to contribute a PR for your proposal? Otherwise, I can mark it as "contribution wanted".

Thanks.

[vfdev-5]

Hi @Nic-Ma , sure I can give it a try.