* 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

* API2.0 del old api(BilinearTensorProduct) from nn init.py, test=develop

* add import for deprecated, test=develop

* modify deprecated location, test=develop

* fix english doc, test=develop

* Update __init__.py

* Update __init__.py

* Update common.py

* fix english doc, test=develop
Co-authored-by: NChen Weihang <chenweihang@baidu.com>

* add pool2d3d API,test=develop

* add api unitest,test=develop

* fix unittest, test=develop

* fix reviews, test=develop

* return one element when return indices is true, test=develop

* fix low converage; to_variable to to_tensor, test=develop

* sort API params, test=develop

* fix en doc, merge PR#26108 to here, test=develop

* fix en doc, 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 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

* add Class KLDivLoss and function kl_div

add the api and doc for the margin_ranking_loss and MarginRankingLoss

add pairewise distance for the paddlepaddle api 2.0

* add Pad2D and Leaky_ReLU, test=develop

* update,test=develop

* change name,test=develop

* add unittest and redine docs,test=develop

* test=develop add linear interpolate operator

* define fluid alias in paddle.tensor and paddle.nn dir test=develop

* from layer import loss in paddle.nn dir test=develop

* add approximation for gelu, test=develop

* add functional conv

* add test and doc for function convs, test=develop

* update ConvTransposeOp's InferShape and error message, test=develop

* add hsigmoid, row_conv in paddle.nn(functional and layer), test=develop

* fix hyperlinks in docstring

* add instance_norm op for dygraph, test=develop

* add error message, test=develop

* add Conv/ConvTranspose layers in paddle.nn.layer, test=develop

* add example code in docstring, test=develop

* update unittests to work with test_runner, test=develop

* add L1Loss

* support L1Loss, test=develop

* add test, test=develop

* fix batch, test=develop

* follow comments, test=develop

* fix high level API(Inference) bug

* patch the unit tests

* Use for_test=True in the Fluid Trainer to clone the test program

* fix typo

* Should do the samething to the inferencer