* support save best based on multi metrics

* add unit test

* resolve bugs after rebasing

* revise docstring

* revise docstring

* fix as comment

* revise as comment

* fix bug of not save-best in iteration-based training

* revise the unit test

* [Feat] Support save best ckpt

* reformat code

* rename function and reformat code

* fix logging info

* support resume from ceph

* move func and refine

* delete symlink

* fix unittest

* perserve _allow_symlink and symlink

* [Fix] Fix some bugs in hooks and runner.

* fix markdown

* fix latex formula

* resolve comments

* Add pyupgrade pre-commit hook

* fix ut

* remove comments

* [Enhance] Make loop related attributes to be runner's properties.

* move iter and epoch to loop

* resolve comments

* change CheckPointHook before_run to before train

* using tmp_path in each checkpointhook test case

* [Refactor] Refactor data_batch type.

* fix sampler

* [Refactor] Remove cur_dataloader in runner.

* fix set_epoch

* [Enhancement] refactor base data elment

* fix comment

* fix comment

* fix pop not existing key without error

* [Refactor] Add batch_idx to hook input.

* update

* [Feature]: Add dist semantics in checkpoint hook

* [Fix]: Delete sync buffer in checkpoint hook

* [Refactor] Refactor interface of checkpointhook

* fix print format

* minor ifx

* Fix hook

* Fix

* Fix docs

* FIx

* Fix

* Fix as comment

* update

* Fix hook

* Fix hook

* Fix hook

* Fix itertimerhook

* Fix iter_timer_hook

* Fix

* Fix

* fix logger hook

* Fix loggerhook

* update cur_dataloader

* Fix docstring

* Fix docstring

* Fix as commet

* Fix as commet

* Fix as comment

* rename is_last_epoch, enhance and add after_val before_val .etc

* fix typo in docstring

* remove resolved TODO

* refactor docstring

* Fix hook

* Fix

* Fix docs

* FIx

* Fix

* Fix as comment

* [Fix]: Change after inter and epoch to after train iter and epoch

* [Fix]: Add new UT to param scheduler hook

* [Fix]: Change the type of runner in docstring to Runner

Co-authored-by: Your <you@example.com>

* [Fix]: Fix data batch type in base hook

* [Fix]: Fix the type hint bug in checkpoint, optimizer, param scheduler hooks

Co-authored-by: Your <you@example.com>

* [Feature]: Add checkpoint hook

* [Fix]: Fix lint

* [Fix]: Delete redundant optional and give an example to our_dir

* [Feature]: Add test the last_ckpt in UT

* [Fix]: Fix docstring problem

* [Fix]: Add patch to UT

* [Feature]: Add Test case for by epoch