* [remove fluid] under fleet meta_optimizers

* [remove fluid] under fleet meta_optimizers

* [remove fluid] under fleet meta_optimizers

* [remove fluid] under fleet meta_optimizers

* [remove fluid] under fleet meta_optimizers

* [remove fluid] under fleet meta_optimizers

* [remove fluid] under fleet meta_optimizers

* [remove fluid] under fleet meta_optimizers

* [remove fluid] under fleet meta_optimizers

* [remove fluid] under fleet meta_optimizers

* [remove fluid] under fleet meta_optimizers

* [remove fluid] under fleet meta_optimizers

[CodeStyle][F821] fix undefined variables due to missing imports, misspelled variable names (#47899)

* `hann` -> `_hann`

* `false` -> `False`

* a missing passed argument `reduce_all`

* some missing imports

* `device_type` -> `heter_device_type`

* `PKVClient` -> `KVClient`

* fix some typos and missing imports

* add recompute doc.

* add recompute doc.

* add recompute doc.

* update.

* update.

* fix flake8 CodeStyle E266

* fix comments

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

* fix an increment

* [CodeStyle][E262][E265] make comments start with `# `

* flake8 config

* support sharding stage2 + mp hybrid_parallel.

* fix the group of check_nan_inf.

* update hcg.

* [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

* add unbalanced data

* fix utest

* [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)`

* [CodeStyle][E712] use `if cond`/`if cond is True` for comparison with `True`

* revert changes in fluid

* revert unrelated file

* revert changes in norm

* revert changes in auto_parallel_amp

* fix norm and auto_parallel_amp

* revert a typo fix due to fixed at #47477

* [CodeStyle][py2] remove `six` package (part2)

* six.ensure_str

* remove unused `import six`

* remove six from BUILTIN_LIKELY_MODULES

* remove six in example code

* remove some decode

* try to fix example code

* fix MockEtcdClient get/get_prefix returns data type

* fix MockEtcdClient get_prefix returns data

* fix MockEtcdClient get returns data

* remove `six` in pypi and conda requirements

* fix MockEtcdClient add_watch_callback/add_watch_prefix_callback returns data type

* refine MockEtcdClient

* add fused_allreduce_gradients_with_group

* add scale

* fix ci

* Fix F522: remove unused arguments

* add redirect_stderr argument in _run_cmd

* update config

* re-blacken python code

* temporarily disable date and diff_py_file

* skip a format

* Fix W605 in tools folder by adding escape symbols

* Fix W605 in incubate and some other folders

* Fix W605 in /fluid/test folders

* Update tools/analysisPyXml.py
Co-authored-by: NNyakku Shigure <sigure.qaq@gmail.com>

* Add some changes to manual and auto escape symbols

* revert changes in transformer.py

* Fix new code with W605 error: add escape symbols

* revert changes in transformer.py

* revert changes in transformer.py
Co-authored-by: NNyakku Shigure <sigure.qaq@gmail.com>

* add test for stage2 + dp

* update test for stage2 + dp.

* update.

* update.

* Fix bug of reduce_sum op. When input.numel() > INT32_MAX, its result
is wrong.

* Support allow_partial switch, which can be configure in
pipeline_configs. If sent tensor are not the same from
different hosts, they shouldn't been sent partially and
then concated as a whole tensor.

* Change name allow_partial to enable_partial_send_recv.

* Add global variable _enable_partial_send_recv

* Fix bug of reduce_sum op. When input.numel() > INT32_MAX, its result
is wrong.

* support pure bfloat16

* support bf16 linear

* update PR to pass CI

* tiny fix where_grad_kernel.cu

* Support bfloat16 type for reducer and sharding.

* Fix some bug.

* Polish code.

* Polise code.

* Add bfloat16 datatype in fill_grad kernels.
Co-authored-by: Nsneaxiy <sneaxiy@126.com>

* combine dp and stage2 hybrid parallel.

* update condition.

* [Zero-Dim] support input 0D Tensor for unary api

* fix CI