* add unique doc

* Add chinese and english documents of paddle.prod

test=develop

* refine sign tanh api, test=develop

* Add Tanh, test=develop

* fix en, test=develop

* 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`

fix unstack cn doc

 Fix the compare ops doc for the api2.0

fix nce docstring for python 3

fix reorder_lod_tensor_by_rank example

Fix the doc examples for those apis

* modify the doc, test=develop

test=develop

* support LoDTensorArray

* fix comma

* add example of LoDTensorArray

* fix typo

* rewrite the sigmoid_focal_loss code example. test=develop

* fix spelling mistake in comments of code example.test=develop