* [CodeStyle][py2][U004] unecessary explicit `object` inheritance in class definition

* fix an increment

* [CodeStyle][py2][U008] remove unnecessary args in `super()`

* remove remained args

* revert changes in test_pylayer_op

* Revert "revert changes in test_pylayer_op"

This reverts commit ff185a9ae738afac3b0264f61bde6c6b7f72e7c4.

* revert some changes in example code

* [CodeStyle][E711] use `is`/`is not` for comparison with `None`

* `self.assertTrue($A is None)` -> `self.assertIsNone($A)`

* `self.assertTrue($A is not None)` -> `self.assertIsNotNone($A)`

* `self.assertFalse($A is None)` -> `self.assertIsNotNone($A)`

* `self.assertEqual($A, None)` -> `self.assertIsNone($A)`

* `self.assertNotEqual($A, None)` -> `self.assertIsNotNone($A)`

* 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

* [PSLIB] Add Metrics Module, Support User-defined Add Metric

* [PSLIB] Modify According to CI

* [PSLIB] Modify According to CI

* [PSLIB] Modify According to CI

* [PSLIB] Modify According to CI Coverage

* [PSLIB] Modify According to CI

* [PSLIB] Modify According to CI

* [PSLIB] Modify According to CI

* [PSLIB] Modify According to CI

* [PSLIB] Modify According to CI

* [PSLIB] Modify According to CI Coverage

* [PSLIB] Modify According to CI Coverage

* [PSLIB] Modify According to CI Coverage

* modify role_maker

* update CMakeLists.txt

* heter bug

* format

* format

* push multi node

* multi node

* MultiThread

* remove log

* solve bug in 30829

fleet support paddle.optimzier

* bug fix

* fix fleet_base

* bug fix

* fix coverage

* add gloo initializer, test=develop

* test=develop, rm netifaces

* add gloo initializer, test=develop

* Support Heter Parameter Server

* move paddle.fleet to paddle.distributed.fleet

* test=develop,test=document_fix, remove the out args

* fleet_util move to paddle.fleet
Co-authored-by: NWuHaobo <wuhaobo1994@gmail.com>
Co-authored-by: Ntangwei12 <tangwei12@baidu.com>

* add heter ps mode

* code style
test=develop

* add with_pslib
test=develop

* unitest
test=develop

* code style
test=develop

* code style
test=develop

* code style
test=develop

* code style
test=develop

* code style
test=develop

* code style
test=develop

* code style
test=develop

* code style
test=develop

* test monitor
test=develop

* prepare trainer
test=develop

* code style
test=develop

Integrated Trainer of Parameter Server (API add `fluid.contrib.layers.sparse_embedding` only) (#22957)

* Integrated Trainer of Parameter Server

* add mock barrier all
test=develop

* fix
test=develop

* fix
test=develop

* fix
test=develop

* add timeout and http store in communication, add revert and confirm in fleet
* test=develop

* fix judge pslib & ranspiler

This reverts commit 66fce9e8.

Fleet Parameter Server API Integrated

* add GeneralRoleMaker which is for general usage
* test=develop

* fix some typos in AMP. test=develop

* delete useless codes. test=develop

test=develop

* fix PaddleCloud Role maker & add warning in distribute transpiler  & change rpc_retry_times

* optimize cloud rolemaker, test=develop

Fix float16 optimizer

* fleet api add input check, test=develop

node_num is not needed for users, so remove them and fix the bugs about it!

Polish fleet API to support cuda collective mode and nccl2 mode

* support filelist size < trainer num
* pull dense when stop, to make sure local dense params are same as pserver, so save paddle model will save dense model same as pserver
*  enable QueueDataset train same filelist for serveral times