* [Fix]: Fix resume bug

* [Fix]: Change last_checkpoint check logic

* [Fix]: Fix lint

* [Fix]: Change warning to print_log

* support resume from ceph

* move func and refine

* delete symlink

* fix unittest

* perserve _allow_symlink and symlink

* [Feature] Add checkpoint helper

* minor fix

* add comments and fix format

* add hub directory

* add missing docstring