* [Feature]: Add parameter schedulers.

* update

* update

* update

* update

* add docstring to lr and momentum

* resolve comments

* add unit tests of data abstract interface

* update

* update

* update docs of data element

* a draft of UT of datasample, to be finished

* update datasample test

* updata

* update

* fix comments

* fix comments

* fix comments

Co-authored-by: liukuikun <liukuikun@sensetime.com>

* tmp

* add scheduler unit test

* disable yapf

* add more test

* add more test

* not use torch test case

* solve comments

* update file

* add more unit tests

* resolve comments

* update cosine ut

* fix typo

* solve comments

* solve comments

* resolve comments

* move fileio directory from utils

* remove CephBackend from fileio and clear some deprecated docstring

* fix format

* fix a spellling error

* tmp commit

* add unittest for basedataset

* fix lint

* resolve all comments

* update

* update

* update

* update

* update

* update

* update

* resolve comments

* resolve comments

* update

* resolve comments

* resolve comments

* Add the unittest of registry

* improve the format

* fix the test_repr

* refactor the test_init

* add the copyright for tests directory

* add more unit tests

* fix error

* add unit tests for _search_child and _get_root_registry

* build_from_cfg supports dict, ConfictDict and Config

* improve docstring