* fix layers. ==> fluid.layers. (#688)

* fix data_reader_cn and dataset_cn (#685)

* fix textual content

* fix issue #682 3 3.2

* fix issues in conv

* Fix io_cn (#597)

* routine bug fix

* update text info

* fix io_cn all

* 持久性变量=>长期变量

* 1220 improve cnapi (#509)

* 1220 update cnapi

* Apply suggestions from code review
Co-Authored-By: Nhaowang101779990 <31058429+haowang101779990@users.noreply.github.com>

* refine reader doc (#686)

* update VisualDL README to add more details (#694)

* improve save_load_variables cn (#689)

* improve save_load_variables

* Update save_load_variables.rst

* fix typo of models (#698)

* fix typo of models

* fix en

* Fix arguments according to 1.3 en + ceil,floor 翻译 +operator 翻译 (#695)

* Fix arguments according to 1.3 en + ceil,floor trans +operator trans

* fix LoDTensorArray spell

* update_reading_data (#699)

* add api_guides low_level backward parameter program_en (#696)

* add api_guides low_level backward parameter program_en

* Apply suggestions from code review
Co-Authored-By: Nzy0531 <48094155+zy0531@users.noreply.github.com>

* Apply suggestions from code review
Co-Authored-By: Nzy0531 <48094155+zy0531@users.noreply.github.com>

* Update backward_en.rst

* Update parameter_en.rst

* Update program_en.rst

* Update doc/fluid/api_guides/low_level/program_en.rst

* add dataset api_cn (#673)

* rm fluid.core in desigin_idea (#674)

* Update fluid_design_idea.md

* Update fluid_design_idea_en.md

* Fix array_read code example error. (#671)
Signed-off-by: Nzhaoyuchen <zhaoyuchen01@baidu.com>

* add data_reader_cn (#676)

* fix doc error (#675)

* update_book_commitid (#680)

* update_book_commitid

* commitid0309

* fix typo

* book indexes (#677)