* Fix ErrorClipByValue api and demo code of clip_by_value. test=develop
Co-authored-by: Ntianshuo78520a <707759223@qq.com>

* Fix example code of api `fluid.layers.switch_case` to use api2.0

* delete `paddle.nn.switch_case` alias and add `paddle.static.nn.switch_case`

* Fix example code of api fluid.layers.case

* delete paddle.nn.case alias and add paddle.static.nn.case

* fix typo for interp_v2,test=develop

* align with torch, test=develop

* add area mode, test=develop

* fix bug, test=develop

* format notes, test=develop

* update for converage, test=develop

* fix bilinear, test=develop

* fix bicubic, test=develop

* fix typo, test=develop

* fix coverage, test=develop

* fix helper.input_dtype, test=develop

* polish notes, test=develop

* polish notes, test=develop

* polish notes, test=develop

rename Dropout2D/3D to Dropout2d/3d

* Add RNN related apis in paddl.nn
test=develop

* new rnn api, cell almost done

* add new progresses in rnn APIs for 2.0

* refine rnn APIs and docstrings.

* add unittets

* disable gpu tests when paddle is not compiled with cuda support

* remove unnecessary imports

* fix docstring

* add to no_sample wlist

* backport to python2 to avoid yield from

* add **kwargs, fix typos

* update docstrings for birnn

* rename argument for SimpleRNN and SimpleRNNCell, fix sample code

* add default value for initial_states in fluid.layers.birnn
Co-authored-by: Nguosheng <guosheng@baidu.com>

* add intepolte_v2

* fix linear interp

* polish unittest, test=develop

* update code samples to 2.0 API, test=develop

* remove warning, test_develop

* add name in attrs, test=develop

* polish code, test=develop

* change Align to align, test=develop

* fix unittest in py3,test=develop

* fix coverage, test=develop

* fix coverage, test=develop

* fix for windows ci, test=develop

* fix coverage, test=develop

* add norm 2.0 api, test=develop

* add norm 2.0 api, test=develop

* add norm 2.0 api, test=develop

* add norm 2.0 api, test=develop

* add norm 2.0 api, test=develop

* add norm 2.0 api, test=develop

* add norm 2.0 api, test=develop

* add norm 2.0 api, test=develop

* add norm 2.0 api, test=develop

* add norm 2.0 api, test=develop

* add norm 2.0 api, test=develop

* add norm 2.0 api, test=develop

* add norm 2.0 api, test=develop

* add norm 2.0 api, test=develop

* add norm 2.0 api, test=develop

* add norm 2.0 api, test=develop

* add norm 2.0 api, test=develop

* add norm 2.0 api, test=develop

* api2.0 paddle.nn.Bilinear and paddle.nn.functional.bilinear, test=develop

* api2.0 fix code examples, test=develop

* modify test_bilinear_api, about place,to_tensor , test=develop

* re pass pre-commit, test=develop

* Update common.py

* fix BilinearTensorProduct ci error, test=develop

* Add MultiHeadAttention api.
test=develop

* Add MultiHeadAttention cache type and gen_cache.
test=develop

* Add TransformerEncoderLayer and TransformerEncoder.
test=develop

* Add Transformer decoder apis.
test=develop

* Add Transformer api.
test=develop

* add unittests for transformer api

* add unittests for transformer api

* Fix some bugs in Transformer apis.
test=develop

* add unittests for encoder, decoder and transformer

* clean conflicts infor in code

* clean Chinese comments

* Add TransformerDecoderCell and TransformerBeamSearchDecoder.
test=develop

* Remove TransformerDecoderCell and TransformerBeamSearchDecoder temporarily.
test=develop

* Add import for Transformer apis.
test=develop

* Update usage of weight_attr and Tensor in Transformer api docs.
test=develop

* Update Transformer apis by renaming MultiheadAttention and cal_kv according to comments.
test=develop

* Fix MultiHeadAttention in test_transformer_api.py.
test=develop
Co-authored-by: NLiuChiaChi <709153940@qq.com>

* add alpha_dropout in nn.functional and nn.layer, test=develop

* refine Interface and assertion, test=develop

* fix ci import error, test=develop

* fix alias and use layers.scale, test=develop

* fix doc and training params, test=develop

* refine details in doc, test=develop

* fix doc details, test=develop

* update Conv2d Conv3d conv2d conv3d api

* update conv_transpose api

* add binary cross entropy with logit loss

* [API2.0] add dropout, dropout2d and dropout3d, test=develop

* refine Interface and assertion after review, test=develop

* fix alias p=1 and use scale, test=develop

* fix doc and training, test=develop

* fix doc in Dropout2D, test=develop

* add functional ctc_loss and CTCLoss class.

* modified docstring of ctc_loss and CTCLoss

* add adaptive_avg_pool2d

* add adaptive_avg_pool3d

* add weight_norm, test=develop

* Rename `Input` into `InputSpec`

* fix argument place of Input api

* add pad func

* add pad

* test=develop, add pad op and apis

* restore pad2d

* test=develop, fix paddl declare

* fix pad interface

* test=develop, fix pad

* test=develop, add all pad api and cos_sim

* test=develop, remove padding default value

* test=develop, rename var to tensor

* test=develop, add more tests

* test=develop, rename tovar to totensor

* test=develop, fix init

* test=develop, add more test

* test=develop, add more tests

* add SyncBatchNorm,test=develop

* logsigmoid and LogSigmoid, test=develop

* add elu gelu relu, test=develop

* update to_variable to to_tensor, test=develop

* address review comments, test=develop

* address review comments, test=develop

* change to_variable to to_tensor in test, test=develop

* add Class KLDivLoss and function kl_div

add the api and doc for the margin_ranking_loss and MarginRankingLoss