GitLab

* [Misc] clang-format auto fix.

* blabla

* ablabla

* blabla
Co-authored-by: Steve <ubuntu@ip-172-31-34-29.ap-northeast-1.compute.internal>

* replace

* blabla

* balbla

* blabla
Co-authored-by: Steve <ubuntu@ip-172-31-34-29.ap-northeast-1.compute.internal>

* param

* brief

* note

* return

* tparam

* brief2

* file

* return2

* return

* blabla

* all
Co-authored-by: Steve <ubuntu@ip-172-31-34-29.ap-northeast-1.compute.internal>

* [Feature] enable to save graphs in multiple formats

* use StreamWithCount to accomodate formats

* fix lint

* fix dynamic cast issue

* fix lint

* refine docstring and code naming

* update docstring

Co-authored-by: Minjie Wang <wmjlyjemaine@gmail.com>

* 111

* add history version test

* fix

* 111

* save

* ``

* fix1

* 111

* add save heterograph

* lint

* lint

* add tests

* minor fix

* fix

* docs

* add format tets

* use unique_ptr

* fix

* fix interface

* 111

* 111

* fix

* lint

* fix

* add support to s3

* fix

* fix

* fix leak

* fix

* fix docs

* fix

* linlt

* fix

* fix

* fix

* address comment

* address comment
Co-authored-by: Minjie Wang <wmjlyjemaine@gmail.com>
Co-authored-by: xiang song(charlie.song) <classicxsong@gmail.com>