* add reference link of elementwise_pow. test=document_preview

* fix Chinese doc of four API. test=develop, test=document_preview

* fix optional argument.  test=develop, test=document_preview

* fix cn doc accoring to reviews. test=develop, test=document_preview

update the has_nan cn_api doc

alter tensor LoDtensor to Tensor LoDTensor

update cumsum api doc

add Tensor/lodTensor for input x description

alter the optional for parameters have default value

test=develop
Signed-off-by: Nzhaoyuchen <zhaoyuchen01@baidu.com>

* fix argsort doc
test=document_preview

* fix
test=document_preview

* test=document_preview

* fix
test=document_preview

* fix
test=document_preview

* fix argmax doc
test=document_preview

* fix
test=document_preview

test=develop
Signed-off-by: Nzhaoyuchen <zhaoyuchen01@baidu.com>

* modify L1DecayRegularizer, L1Decay, L2DecayRegularizer and L2Decay, test=develop

* update cn doc for ones and zeros op

* fix the types of shape in zeros op

* add return type for ones and zeros op

* list all supported data types for zeros and ones op

* improve seq_concat seq_conv e.t api cn doc

* refine doc

* add datatype

* refine doc for api Program, BackwardStrategy, default_start_up_program

* remove wrong binary char to make file not binary

* delete binary file and push a new file as regular one

* change name back since we delete bianry Program_cn on develop

* refine clone doc

* remove additional gitignore

* refine doc about some info

* refine doc about some info

* refine doc about some info

* refine doc about some info

* refine doc about some info

* remove useless info

* refine doc

* fix code

* fix doc error in Program_cn.rst

*  add code and refine doc

* refine clone doc

* add instance norm

* refine switch doc, test=develop, test=document_preview

* add description and sample for member functions, test=develop

* Rewrite the content of load_persistables_cn.rst.

* refine the fill_constant doc test=develop

* fix according the standard test=develop

* fix fill_constant doc test=develop

* fix from standard test=develop

* refine api comments

* refine api comments

* update docs

* update docs

* Rewrite the content of the chain in Reader_cn.rst.

* refine While doc, test=develop

* add refine Switch api doc, test=develop

* refine While, delete Switch, test=develop, test=document_preview

* refine api docs of scale, selu, shape, split, soft_relu. test=develop, test=document_preview

* refine sample codes for api docs, test=develop

* add result comments for sample codes, test=develop

* refine api_cn, test=document_preview

* update cn doc for floor op

* refine the description of floor op

* fix reciprocal doc spec test=develop

* fix doc test=develop

* fix according reviewer advice test=develop

* fix according the review advice test=develop

* fix according the review advice test=develop

* Rewrite the content of load_params_cn.rst.

* use default_main_program instead of _main_program_.

* fix fill_constant_batch_like doc test=develop

* fix doc test=develop

* fix typo test=develop

* fix according reviewer advice test=develop

* fix according review advice test=develop

* Refine fsp_matrix/deformable_conv/fsp_matrix/polygon_box_transform api.

* fix argmin doc
test=document_preview

* test=document_preview

* fix
test=document_preview

* fix relu6 doc
test=document_preview

* fix threshold

* fix
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* fix relu doc
test=document_preview

* fix relu doc

* fix
test=document_preview

* update save_vars and load_vars, test=develop

* modify L1DecayRegularizer, L1Decay, L2DecayRegularizer and L2Decay, test=develop

* add black lines, test=develop

* Rewrite firstn and shuffle functions, test=develop

* improve seq_pool api cn doc test=document_preview

* refine sequence last and first pool doc test=document_preview

* refine sequence_pool dataType test=document_preview

* fix input dtype

* add dataType

* fix datatype

* update LoDTensor_cn.rst, test=document_preview

* update LoDTensor_cn.rst, test=document_preview

* update description of LoDTensor

* follow comments

* refine doc: pool2d/3d, adaptive_pool2d/3d, grid_sampler, kldiv_loss,
spectral_norm, temporal_shift. test=document_preview

* refine doc: exponential_decay, inverse_time_decay, natural_exp_decay. test=document_preview

* refine doc. test=document_preview

* refine doc for learning_rate_scheduler. test=document_preview

* refine OP. test=document_preview

* fix kldiv_loss. test=document_preview

* fix spectral_norm formula. test=document_preview

* Fix cn doc of some api:
1. affine_grid
2. generate_proposal_labels
3. generate_proposals
4. rpn_target_assign
5. warpctc

* fix the reduce api test=develop

* fix typo test=develop

* fix according reviewer advice test=develop

* fix doc for PipyReader test=develop

* fix doc for PipyReader test=develop

* fix according reviewer advice test=develop