* add feature to fleet2.0 role_maker, distribute_strategy, test=develop

* add check approval
test=develop

* make fleet_localsgd_meta_optimizer work

* fix bug in localsgd meta optimizer

* set default value to strategy in distributed_optimizer test=develop

* print user-friendly error message

* adjust error sumary

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

* add nll loss API, update demo code of the comment

* upate the target to label, test=develop

* Update the code for the margin_ranking_loss, test=develop

Update the sigmoid, Sigmoid layer for the api2.0

* Fix build whl package

* del timestamp

* fix

* Update `paddle.add`

remove `alpha`
update doc sample code
remove `:alias` etc

* Remove `imperative` reference from docstring

* fix test_multiprocess_dataloader unittest. test=develop

* add children and named_children

* adaptive expand op to 2.0 (align to torch.expand) , test=develop

test=develop

* expose and unify the Tensor concepts to the user

* expose tensor to user

* add copy place for Tensor

* add copy place for Tensor

* add note

* add macro PADDLE_WITH_CUDA

* remove RUN_TYPE=DIST

* fix some error

* add tile_op, test=develop

* add Class KLDivLoss and function kl_div

* show deprecation warning once

* add some notes

* remove unused module

* test=develop, bug fix for test_dist_fleet_ctr

* add paddle.nn.functional.mse_loss

* add name

* fix conflict

test=document_fix

remove activation wording

test=develop,test=document_fix

remove activation wording

test=develop,test=document_fix

remove activation wording

test=develop,test=document_fix

remove activation wording
tanh -> tan

test=develop,test=document_fix

explain input/out put range and out of boundary behavior

* Upgrade `no_grad` decorator

test=develop

- match torch decorator usage (i.e., with parenthesis)
- handle generator functions
- add `paddle.no_grad` alias

* Switch from `functools` to `decorator`

preserves signature

* Reword decorator usage note