* replace layers.cross_entropy with paddle.entropy

* fix args

* fix codestyle

* remove flatten in nn.py under fluid

* fix test case

* fix test case

* fix codestyle

* fix codestyle

* fix code style

* remove extra test case

* remove test case

* fluid clean move out LayerList, ParameterList, Sequential from fluid

* copy Sequential from fluid to paddle.nn

* replace fluid LayerList,ParamterList, Sequential in unit test file

* add omit unit test file use paddle.nn.Sequential

* remove numpy and use paddle.uniform instead

* [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

* update config

* re-blacken python code

* temporarily disable date and diff_py_file

* skip a format

* change fluid.mean to paddle.mean

* reverse some old code examples

* 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

* PTQ save quantized model

* Wrap simulated layer

* post process the inference model

* Add wrap for functional api
* Refine the wraped api
* Add unit test for quant functional layers
* Update all unit tests for dygraph qat