* test=develop, add addmm doc

* add addmm doc

* test=develop, add addmm doc

* test=develop, add pad doc

* restore addmm

* test=develop, add pad

* test=develop, fix pad interface

* test=develop, add pad eng doc link

* test=develop, add other pads

* test=develop, remove pad default

* test=develop, fix const pad1d code

* test=develop, fix var

* test=develop, fix pad typo

* test=develop, rename tovar to totensor

* test=develop, fix code

* test=develop, fix typo

* test=develop, fix cos_sim interface

* test=develop, fix typo

* modify the doc, test=develop

* refine bceloss doc

* fix doc

* fix name

* fix api 2.0 directory migration

* add dir file and change x to input

* add doc of loss function binary_cross_entropy.

* delete static demo code.

* Update `paddle.clamp` doc

rename to `paddle.clip`
`input` -> `x`
remove `out`
update samples
wording: `Variable` - > `Tensor`

* Apply template

* Update `enable_imperative` -> `disable_static`

* Update sample: `to_tensor`

* modify the doc, test=develop

* add 2/3d adaptive_pooling

* fix format

* fix format

* add en doc rst

* fix format

* fix doc

* fix doc

* refine example code

* unify example code

* Udpate the doc format for the paddle, test=develop

* modify nn.data into static.data

* Update index_cn.rst

* nn.data to static.data

* remove alias

* rename the inputs and update code example, test=develop

* update doc

* polish some docs

* polish some docs

* Update square_cn.rst

* polish some docs

* polish some docs

* polish round docs

* polish round docs

* Update square_cn.rst

* polish some docs

* polish functional_cn.rst

* add DataParallel cn doc

* polish details

* fix method declarative error

* polish format

* fix sample code error

* append to white list

* polish some docs

* polish some docs

* Update square_cn.rst

* polish some docs

* polish some docs

* polish round docs

* polish round docs

* Update square_cn.rst

* remove the out args

* polish sqrt doc

* Update sqrt_cn.rst

* Update sqrt_cn.rst

* Update sqrt_cn.rst

* Add Chinese documents for api paddle.fluid.dygraph.enabled, test=develop, test=document_fix

* Add Chinese documents for api paddle.fluid.dygraph.enabled 2, test=develop, test=document_fix

* Add Chinese documents for api paddle.fluid.dygraph.enabled 3, test=develop, test=document_fix

* Add Chinese documents for api paddle.fluid.dygraph.enabled 4, test=develop, test=document_fix

* add mse_loss_cn doc

* add index

* add index

* Update `paddle.add` docs

remove `out` and `alpha`
explain broadcast semantics
update doc samples

* Apply template and fix alias

* Add DecodeHelper cn docs.

* Update Seq2Seq API cn doc.

* Fix BasicDecoder sample code.

* Fix TrainingHelper, GreedyEmbeddingHelper, SampleEmbeddingHelper and BasicDecoder sample code in cn docs.

* Add cholesky api cn docs.
Co-authored-by: NFrostML <380185688@qq.com>

* Update docs for `abs` `acos` `asin` `atan` `ceil` `cos`

update code samples
`Variable` -> `Tensor`
remove activation wording
explain cos input/output range
misc fixes

* Apply input template

* Update `enable_imperative` -> `disable_static`

* Update `no_grad` docs

add alias `paddle.no_grad`
use `paddle.no_grad()` for decorator usage
update code sample

* Fix alias

* Reword decorator usage note

* remove the out args

* update log docs

* update log1p docs

* test add api

* add_api test=develop

update the margin rank loss api doc

fix unstack cn doc

update demo code in NLLLoss_cn.rst

* add pairwise distance cn docs

* fix link

* add alias

* refine format

* fix doc tree

* fix format

* add name

* change out -> output

* change eps -> epsilon

* fix name

Update the docs of nn.loss.L1Loss and nn.functional.l1_loss