* update 2.0 public api in nn

* replace Chinese character cause error in ci;synchronization with pr:#32588 to avoid 'ascii' codec in python2

* numbers used in paddle.nn.functional.norm but not imported

* fixed docs.

* Fixed docs. test=document_fix

code bak.

fixed docs. test=document_fix

* Revert to previous version of python/paddle/fluid/backward.py

* fixed bugs.

* test=document_fix. Fixed examples.

* fix cross_entropy calculation error

* add unittest and fix static

* Support list and tuple for parameters of layer_norm, multiprocess_reader, DatasetFolder and ImageFolder.

* add unittest for layer_norm.

* add require gpu for example.

* Modified params of some APIs to support tuple and list.

* fixed bug.

* add norm_by_times param to ctc_loss

* fix doc,test=develop

* import sequence_* API to new namespace

* fix typos, remove alias marking

* update sample code

* fix sample code

* fix docstring for sequence_mask

* modify conv2d_transpose docs

add glu in nn.functional

* improve performance of DepthwiseConv(NWHC)

* fix test of affine_grid with rocm

* fix test of affine_grid with rocm

* fix en doc for emb, test=document_fix;
Change-Id: I4757e67caacd7189f068493ed45a7445f87ffb40

* add deprecated for softmax_with_cross_entropy, test=develop

* test for deprecated in english doc, test=develop

* test deprecated for softmax_with_cross_entropy in english doc, test=develop

* fix readme and English doc for cross_entropy, test=develop

* rm test for softmax_with_cross_entropy deprecated, test=develop

* update readme for CrossEntropyLoss, test=develop

* fix readme format, test=develop

* fix readme format, test=develop

* fix readme format for cross_entropy, test=develop

* add softmax_switch and fix softlabel for cross_entropy, test=develop

* 1)recovery softmax_with_cross_entropy in fluid 2) change softmax_switch to use_softmax 3) add example for softlabel for cross_entropy, test=develop

* fix Example number for cross_entropy, test=develop

* fix code format, test=develop

* fix for CI-Coverage, test=develop

* fix for CI-Coverage, test=develop

* fix ci-coverage for Non-ASCII character '\xe2' in file, test=develop

* fix ci-coverage for Non-ASCII character '\xe2' in nn.layer.loss.py, test=develop

* update description for doc when use_softmax=Fasle, test=develop

* fix some docs and code example for cross_entropy, test=develop

* delete redundant description for soft_label parameter of cross_entropy, test=develop

* fix some comment for test_cross_entropy_loss.py, test=develop

* improve performance of depthwise_conv2d

* add unittest

* support label with float input of cross_entropy, test=develop

* fix code style in nn/functional/loss.py, test=develop

* add view strategy on squeeze,unsqueeze,reshape,flatten

* add squeeze unittest

* add unittests

* use View strategy as name rather than Reuse Allacation

* fix view api doc

* fix format

* use core.ops when input of reshape2 is Tensor

* fix test_cross_entropy_loss error because of reshape2

* fix test_cross_entropy_loss error because of reshape2

* add inplace strategy

* add elementwise_add sub

* let backward op not use inplace

* grad op do not use inplace

* fix memory increase error and add leaf error message

* delete selected_rows

* change op_function

* little change

* solve HandleViewBetweenInputAndOutput

* add unittest and leaf error message

* merge view error

* optimize op_function_generator format and support sum inplace op

* fix format of basic_engine

* fix format for framework

* little change of variable wrapper

* add reshape, squeeze, unsqueeze, scatter api

* add relu elu tanh softmax inplace api

* fix test_squeeze_op unittest

* fix test_relu_op unittest

* fix comment problems

* delete sample code of inplace api

* add reference of grad_pending_nodes in basic_engine

* fix unittest name

* add inplace apis into wlist

* fix error message

* add PADDLE_ENFORCE for set grad op twice

* fix head file error

* fix bug of using ignore_index and reduction,test=develop

* fix bug of celoss when using ignore_index and reduction, test=develop

* improve performance when ignore_index=-100, test=develop

* add test in test_cross_entropy_loss.py for coverage rate, test=develop

* rm comment in test_cross_entropy_loss.py, test=develop

* del  hard code of "float64" in python/paddle/nn/functional/loss.py, test=develop

* change mask to a more simplified implementation, test=develop

* del comment in python/paddle/nn/functional/loss.py, test=develop

* del hard code and change mask to a more simplified implementation, test=develop

* change mask to a more simplified implementation, test=develop

* change mask to a more simplified implementation, test=develop

* delete paddle.nn.functional.assign

* fix dynamic to static error

* add dispenable input 'shape' for core.ops.reshape2

* add dispenable inputs for core.ops.reshape2/expand/slice

* add ut

* add attribute for batch_norm

* fix code bugs

* fix code bugs test=document_fix

* fix code bugs test=document_fix

* rm check_import_scipy, rm chunk_eval and mean_iou in paddle.metric.__init__.py

* Revert "rm check_import_scipy, rm chunk_eval and mean_iou in paddle.metric.__init__.py"

This reverts commit 179ba8c2b22bc31fe8d8a126e31820792cbd0f4e.

* delete paddle.metric.chunk_eval and paddle.metric.mean_iou

* delete paddle.nn.clip and paddle.nn.clip_by_norm

* delete paddle.nn.functional.activation.hard_sigmoid and paddle.nn.functional.activation.hard_swish

* delete paddle.nn.Pool2D, paddle.nn.BilinearTensorProduct, paddle.nn.RowConv, paddle.nn.functional.row_conv

* fix extension import error

* fix unittest for row_conv and Pool2D

* add fast path for p == 0 in dropout

* add ut

* Fix api docs in RNN, Transformer, layer_norm, WeightNormParamAttr.
test=develop

* Fix api doc for print in label_smooth.
test=develop

* Update api docs according to review comments.
Add name argument in RNN back.
test=develop

* fix multiple documentation error, test=document_fix

* fix more rst syntax errors, test=document_fix

* fix format issues in docstring, test=document_fix

* fix gpu emb out of range

Change-Id: I5794ac73bd634d5ea069a6fbbd914274b6d6b7bf

* fix doc

Change-Id: I5a3350b2930a9ab2f52116c192b087307faf8fdf

* fix nll_loss doc;test=document_fix;

* remove numpy and set_device;test=document_fix;

* remove numpy;test=document_fix;