* no endpoints in dy mode

* fix fleet api inconsistent

* mv all unittests test

* fix error

* fix error

* fix

* fix

* del unittests

* fix paddle_build.sh

* fix

* fix test

* fix add test

* fix

* fix

* fix

* merge develop

* fix

* fix

* fix

* fix

* fix

* merge develop

* fix test_async_read_write

* fix test_async_read_write

* merge develop

* fix

* fix import legacy_test

* fix

* fix

* fix

* fix

* fix

* fix

* fix

* fix

* fix bug

* fix

* fix coverage test bug

* fix

* fix

* fix

* fix

* fix

* fix code sstyle

* fix code

* fix code

* fix

* fix

* fix

* del test_sequence_enumerate_op.py

* fix

[CodeStyle][C408][C409][C410] Fix unnecessary <dict/list/tuple> call and unnecessary <list/tuple> passed to <list/tupule>() (#51928)

* autofix

* add select config

* autofix C410

* add C410 select

* fluid clean: remove parallel and parallel_helper api

* fix: fix the import path.

* fix DataParallel imports issue

* update config

* re-blacken python code

* temporarily disable date and diff_py_file

* skip a format

* [CodeStyle] remove all future import

* revert test_error.py

* restore future import in example code

* use yapf to format all python file

* yapf exclude two unittests file for they rely on writing and reading file, and format will break them

* disable diff_py_file because too many diff files cause command following failed

* fix spawn default nprocs get error

* polish error message

[Kunlun]Multi xpu dygraph performance optimization , add distributed.spawn support for multi xpu and some bug-fixes (#31130)

* Simplify the options of spawn based on fleetrun

* polish details

* polish doc details

* polish parallel api impl & doc details

* add unittest for coverage

* remove spawn test in py2.7

* add parallel api into white list

* remove backend argument of init_parallel_env

* remove keep name table in transformer

* add cpu version check

* add skip unittest for init_parallel_env

* polish doc: remove func use & update example

* add dygraph parallel run interface

* polish implement & unified env property name

* add print config arg

* refactor init_parallel_env function

* Compatible with multiprocessing and launch modes

* set default trainer start port

* support run in python 2

* polish python2 support code

* remove python2 support

* refine launch import

* polish dome design details

* refactor api implemention & path

* use new method _set_expected_place

* add spawn unittest framework & mnist test

* add more unittests & doc

* fix unittest failed

* polish english doc

* self review and polish details

* refactor code by reviewer's comments

* fix unittest failed

* fix parallel_env unittest

* fix several typos

* fix error introduced when fixing typos

* add unpublic note for start_processes

* polish details by xiaoguang's comment

* verify correctly when spawn nprocs=-1

* refactor spawn & init_parallel_env design

* polish doc details

* open spawn unittests

* try to fix doc compile error

* try to fix unknown doc format error

* add skip unittest when not gpu