* split api_spec document;test=document_fix

* change tools

* test=develop;test=document_fix

* test=develop;test=document_fix

* refine print_signatures.py to remove ComposeNotAligned, test=develop

* remove experimental_namespace, test=develop

* fix the api.spec file does not get the class comment problem

* cat new.spec

* check api.spec

* test=develop

add Dygraph api to api.spec

* test=develop

* test=develop

* test=develop

* del #

* Update detection API add new check document

* update API.spec

* test=develop;add shanyi15 approved API.spec

* test=develop;update PM check API.spec

* check api.spec

* test=develop

* update API.spec

* test=develop;update API.spec

* update API.spec

* cat API.spec

* update documnent in api.spec

* check python35 api.spec

* update print_signatures md5 function

* test=develop

* update API.spec

* test=develop;fix python3 API.spec diff

* test=develop

* test=develop

* test=develop

Revert "Merge pull request #14798 from PaddlePaddle/revert-14786-revert-14782-revert-14398-imperative"

This reverts commit b1d3a1c8, reversing
changes made to f1fb64b1.

test=develop

test=develop

test=develop