* support to_static(model)

* add warning and unittest

* add some unittest cases ot verify jit.save, no_test

* add more unittests

* add test with example inputs

* polish implement details

* remove useless blank

* fix fetch random error

* Add naming rule if not specific InputSpec.name

* fix function name typo

* refine comment

* remove print statement

* change configs to config & update examples

* fix deprecate decorator conflict

* add descriptor cache

* fix self arugments

* deal case if instance is None

* clean code

* fix usage

* add TranslatedLayer.program method

* add unittests & update example code

* polish example code

* update program api example code

* update set_dict method name & add aliases

* fix var name error

* fix alias formats

* use set_state_dict in unittest

* add decorator solve compatible problem

* polish decorator

* replace layer set_state_dict by patched method

* remove import monkey path layer

* fix import function error

* add unittest for coverage

* support load infer model format state dict

* add unittests

* remove keep name table

* recolve circle inport

* fix compatible problem

* recover unittest

* polish doc and comment

Raise RuntimeError if run the callable object decorated by '@paddle.jit.to_static' not in dynamic mode.  (#26750)

[Dy2Stat-debugging] Fix bug: Returns True if the verbosity level set by the user is greater than or equal to the log level (#26858)

* update doc

* update doc

* fix optimizer sample code

* add default value for adamw weight_decay

* fix adamw

* change LearningRateDecay to _LRScheduler

* fix adamw;notest

* fix load;notest

* remove file

* bug fix

* fix code style

* bug fix

* add ut

* adamw support weight_decay=0

* fix ut

* fix set_lr doc

* fix doc

* change parameters place

* remove backend argument of init_parallel_env

* remove keep name table in transformer

* add cpu version check

* add skip unittest for init_parallel_env

* polish doc: remove func use & update example

* Fix Python Version compatibility

* add import six

Use `Tensor` instead of `Variable`  in the doc of paddle.grad.

* add dygraph parallel run interface

* polish implement & unified env property name

* add print config arg

* refactor init_parallel_env function

* Compatible with multiprocessing and launch modes

* set default trainer start port

* support run in python 2

* polish python2 support code

* remove python2 support

* refine launch import

* polish dome design details

* refactor api implemention & path

* use new method _set_expected_place

* add spawn unittest framework & mnist test

* add more unittests & doc

* fix unittest failed

* polish english doc

* self review and polish details

* refactor code by reviewer's comments

* fix unittest failed

* fix parallel_env unittest

* fix several typos

* fix error introduced when fixing typos

* add unpublic note for start_processes

* polish details by xiaoguang's comment

* verify correctly when spawn nprocs=-1

* refactor spawn & init_parallel_env design

* polish doc details

* open spawn unittests

* try to fix doc compile error

* try to fix unknown doc format error

* add skip unittest when not gpu

* [Dy2Stat] Add debugging and logging mechanism for dygraph to static. 

* Remove TransformerError temporarily. 

* import mock in PY2, from unittest import mock in PY3. test=develop

* Expose interfaces set_code_level and set_verbosity in paddle.jit, fix doc of the two interface. 

* polish doc of set_verbosity and set_code_level. 

* update the demo code and the doc of varbase.backward.

* update the doc of the fake interface `paddle.fluid.Variable`.

* remove BackwardStrategy.

* add InputSpec

* add unittest for tensorSpec and SimpleNet

* API2.0 del old api(BilinearTensorProduct) from nn init.py, test=develop

* add import for deprecated, test=develop

* modify deprecated location, test=develop

* fix english doc, test=develop

* Update __init__.py

* Update __init__.py

* Update common.py

* fix english doc, test=develop
Co-authored-by: NChen Weihang <chenweihang@baidu.com>

As the title.

* fix syncbn, test=develop

* fix test,test=develop

* fix unittest,test=develop

* add div, floor_div, remainder

* update the demo codes of paddle.grad.

* refine load model by extra_var_info

* polish unittest for coverage

test=document_fix

* binding tensor method

* binding tensor method

* binding tensor method

* Binding methods for class Tensor and Variable

As the title

* enhance add parameter check for layer

* add unittest for coverage

* remove uninit test case

* enrich unittest ccase

* trigger ci check

* add SyncBatchNorm,test=develop