GitLab

* feat: add custom_group to DefaultOptimConstrutor

* refactor: move custom_groups validate to _validate_cfg

* docs: add doc to explain custom_groups

* feat: add unittest for non_exist_key

* refactor: one param per group

* fix: small fix

* fix: name

* docs: docstring

* refactor: change to mult for only lr and wd custom

* docs: docstring

* docs: more explaination

* feat: sort custom key

* docs: add docstring

* refactor: use reverse arg of sorted

* docs: fix comment

* docs: fix comment

* refactor: small modi

* refactor: small modi

* refactor: small modi