Updated BaseOutputHandler to accept state attributes - Tensorboard

[Ishan-Kumar2]

Addresses #2100 (using "fixes" will close the issue)

Description:

Adds feature to log state attributes in Tensorboard

Check list:

• New tests are added (if a new feature is added)
• New doc strings: description and/or example code are in RST format
• Documentation is updated (if required)

[vfdev-5]

Thanks for the PR @Ishan-Kumar2 !
Looks good. I have a suggestion to remove TrainerStateHandler and put the new arg to OutputHandler.

[vfdev-5]

@Ishan-Kumar2 thanks for the update ! I liked the way you handled data type dispatch and I left a comment on how we could improve our loggers.

[vfdev-5]

Thanks for the update @Ishan-Kumar2
There few issues with docstrings otherwise, looks good.

[vfdev-5]

I think these modifications are wrong, take a look how it is rendered now: https://deploy-preview-2137--pytorch-ignite-preview.netlify.app/generated/ignite.contrib.handlers.tensorboard_logger.html#ignite.contrib.handlers.tensorboard_logger.OutputHandler

Let's also update line 177:

- Helper handler to log engine's output and/or metrics
+ Helper handler to log engine's output, engine's state attributes and/or metrics

[vfdev-5]

This line 182 shouldn't be deleted. That's why the docstring is wrongly rendered.

[vfdev-5]

Thanks @Ishan-Kumar2

[vfdev-5]

@Ishan-Kumar2 I forgot to ask you to add .. versionchanged:: as explained here: https://github.com/pytorch/ignite/blob/master/CONTRIBUTING.md#writing-documentation . See as example here:

ignite/ignite/handlers/stores.py

Lines 38 to 39 in c6ff5b8

	.. versionchanged:: 0.5.0
	`attach` now accepts an optional argument `name`

Please send a PR with a fix.

By the way, would you like to update other loggers ?

[vfdev-5]

@Ishan-Kumar2 can you address this comment please for TB and Visdom. Yesterday I also forgot to ask about that. Thanks