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* dist index chapter

* preproc chapter

* rst

* tools page

* partition chapter

* rst

* hetero chapter

* 7.1 step1

* add parmetis back

* changed based on feedback

* address comments

* enable to launch multiple client groups sequentially

* launch simultaneously is enabled

* refine docstring

* revert unnecessary change

* [DOC] add doc for long live server

* refine

* refine doc

* refine doc

* update DistGraph docstrings.

* add user guide.

* add doc string.

* fix.

* fix.

* fix.
Co-authored-by: Jinjing Zhou <VoVAllen@users.noreply.github.com>

* [Doc] Add Chapter 7

* [Doc] Add CN part 7, 7.1, 7.2, and 7.3

* [Doc] Add CN part 7, 7.1, 7.2, and 7.3

* [Doc] 1st round copyediting, 7, 7.1, 7.2, and 7.3, removing EN parts.

* [Doc] 2nd round copyediting.

* [Doc] 3rd round copyediting.

* [Doc] Copyedit with reviewers' comments.
Co-authored-by: Mufei Li <mufeili1996@gmail.com>

* distributed APIs.

* add guide.

* add index.