* rewrite all code examples, test=document_fix

* refine arguments, test=document_fix

* fix desc format error, test=document_fix

* capitalize the first letter, test=document_fix

* refine api desc, test=document_fix

* fix wrong COPY-FROM label in Model docs, test=document_fix

* refine returns, test=document_fix

* refine returns, test=document_fix

* add a blank line in code block, test=document_fix

* add copy-from label for code examples, test=document_fix

* refine docs, test=document_fix

* add some output for code example, test=document_fix

* add `optional`, test=document_fix

* add missing parameters, test=document_fix

* add missing links for `ProgBarLogger` and `ModelCheckpoint`, test=document_fix

* update eval_batch example, test=document_fix

* fix typos in stack_outputs, test=document_fix

* np.random -> paddle.random, test=document_fix

* use yapf to format all python file

* yapf exclude two unittests file for they rely on writing and reading file, and format will break them

* disable diff_py_file because too many diff files cause command following failed

* fix summary trainable_params bug

* docs_epoch1

* docs_epoch1

* update kron api docs

* update erfinv;test=document_fix

* subtract

* for ci;test=document_fix

* [Eager] Support test_dist_hapi_model under eager mode

* [Eager] Polish code

* Fix code-format issue, coverage-ci issue

* refactor eager flags

* fix flags error when we switch from eager to dygraph

* fix ci problem

* fix ci

* fix ci

* merge develop and fix code style

* merge develop and fix code style

* fix op test error

* fix op test error

* fix op test error

* fix op test error

* fix op test error

* merge develop

* switch eager mode and change it

* set default is eager

* set default is eager

* fix error; test=develop

* fix some error; test=develop

* update

* upd

* update code; test=develop

* update

* fix some bug; test=develop

* fix bug; test=develop

* fix bug; test=develop

* fix bug; test=develop

* fix error; test=develop

* format; test=develop
Co-authored-by: NJiabinYang <360788950@qq.com>

* Add loss conversion from uint16 to float in progressbar class

* Fix test coverage

* Actually fix coverage

* Fix format error

* Fix AttributeError when output y is a tuple which has no attribute 'shape'

* Add unit test for dynamic_flops with multiple outputs

* Add unit test for dynamic_flops with multiple outputs

* [hapi] support dygrapg amp O2

* fix problem of static pure fp16 in hapi

* fix bug

* fix format

* fix ut

* follow comments

* update ut

* update amp save/load

* fix ut

* refine code format

* fix warning error , test=document_fix

* fix warning error , test=document_fix

* fix warning error , test=document_fix

* fix warning error , test=document_fix

* fix warning error , test=document_fix

* fix warning error , test=document_fix

* fix warning error , test=document_fix

* fix paddle.summary's bug when output contains non-tensor

* add input option in model.summary

* add num_iters in fit/evalate, test=develop

* del py2 code2

* fix test timeout

* update 2.0 public api in vision

* fix some flake8 errors

* add wget option in download

* add option verbose for predict api

* add progressbar for datasets downloading