* [CodeStyle][py2] remove `six` package (part2)

* six.ensure_str

* remove unused `import six`

* remove six from BUILTIN_LIKELY_MODULES

* remove six in example code

* remove some decode

* try to fix example code

* fix MockEtcdClient get/get_prefix returns data type

* fix MockEtcdClient get_prefix returns data

* fix MockEtcdClient get returns data

* remove `six` in pypi and conda requirements

* fix MockEtcdClient add_watch_callback/add_watch_prefix_callback returns data type

* refine MockEtcdClient

* Extend python einsum interface to make einsum_v2 support multi-operands and switch it to default.

* add opt_einsum dependence

* add yaml and support eager model

* fix by code review

This reverts commit ee813e34.

* reuploaded files

* Changed year from 2021 to 2022

* minor change

* fixed requirements.txt file

* test if numpy=1.19.5 meet unittest's requirement

* modify numpy version required

* test if windows still need numpy <=1.19

* modify acoording to zhouwei's comment

* integrated gast library

* integrated gast library

* fix unittest and remove ast2.py

* remove 'gast' from __all__ in __init__.py

* add copyright in other files

* fix copyright

* [2.0.1]Support New Custom OP on windows

* fix CI

* fix code style

* fix CI

* fix CI

* fix coverage

* fix CI

* fix CI

gast version can be conflict with the other software users installed. We set the version to be higher than 0.3.3

* lazy import for scipy

* rm unused check

* test=develop, rm pathlib

Remove NLTK requirements to avoid dependency security alert from Github Dependabot

* test=develop, rm netifaces

* rm dependence of cv2

* remove objgraph

* remove graphviz

* fix ut

set default python3,fix incompatible,cache dir for third party,unify error code,for windows (#26178)

* set default python3 for paddle windows,test=win

* set default python3,cache dir for third party,error code,test=win

* fix some incompatible

* fix some error

* set virtual environment,test=win

* test=develop,test=document_fix, remove the out args

* fleet_util move to paddle.fleet
Co-authored-by: NWuHaobo <wuhaobo1994@gmail.com>
Co-authored-by: Ntangwei12 <tangwei12@baidu.com>

* support nested if/else

* support to derivate returns the parameter list automatically

* polish tranform function of slice

* fix modify x.numpy()[i] slice function

* support to transform ast.node into callable function

* fix get_name_ids bug and add more unittest test=develop

* fix requirements.txt test=develop

* remove useless import statement test=develop

* Fixed version compatibility issues in param of function test=develop

* use decorater to test ast_to_func test=develop

* add textwrap.dedent for source_code test=develop

* polish code comment

* fix compatibility with python2 and python3 test=develop

* fix gast version error test=develop

* fix gast repo test=develop

* polish transfer_from_node_type code test=develop

* add nested_if_else unittest test=develop

* split IfElseTransformer test=develop

* specify gast version test=develop

* fix ast_to_func root type test=develop

1. Move AstNodeWrapper, StaticAnalysisVisitor to a new python file: static_analysis.py
2. Add basic node var type analysis