* [CodeStyle][F401] remove unused import in python/paddle/distributed

* remove pass

* empty commit

* Fix ValueError: list.remove(x): x not in list for meta_optimizer_names.

Fix ValueError: list.remove(x): x not in list for meta_optimizer_names.

* Fix split import.

Fix split import.

* add noqa after meta_optimizers in factory

* restort collective ops

* expand `import *`

* add noqa after required imports

* try to fix APIs without core.ops

* Revert "try to fix APIs without core.ops"

This reverts commit 6172beaf601e84bf61f2490c12c4739f0edaa5eb.

* fix an increment

* empty commit

* add noqa after required imports

* expand `import *`, fix ci error
Co-authored-by: NShuangchi He <34329208+Yulv-git@users.noreply.github.com>

* refactor mp.

* update setup.py.

* update mp_layers.py for compatibility.

* add documents for mp_layers.py

* update init.py

* update collective.py.

* update.

* update mp_ops.py

* update.

* update code style.

* update code style.

* reconstruct_of_fleet_api

* update

* 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 calling bug of HybridParallelClipGrad

* fix bugs of HybridParallelClipGrad

* add unittest of pp with HybridParallelClipGrad

* fix bugs in mp_layers.py

* update

* fix bugs in pp_layers.py

* update

* add parallel_cross_entropy

* add grad for crossentropy

* fix cross entropy

* fix c_split bug

* fix utest

* add c_embedding for tensorparallel

* fix precision of mp

* fix bug of seed

* fix dp

* print group

* fix model parallel

* rm parallel_help.py

* add embedding

* add pipeline layer

* add model parallel support in dygraph