GitLab

* add distributed in-degree and out-degree.

* update comments.

* fix a bug.

* add tests.

* add tests.

* fix a bug.

* fix docstring.

* update doc.

* fix

* fix.
Co-authored-by: Zheng <dzzhen@3c22fba32af5.ant.amazon.com>
Co-authored-by: xiang song(charlie.song) <classicxsong@gmail.com>