* refactor the optional tensor

* remove optiona<MetaTensor> in InferMeta

* fix bug

* fix optional<vector<Tensor>>

* fix bug

* fix rmsprop

* fix amp of eager_gen

* polish code

* fix deleted code

* fix merge conflict

* polish code

* remove is_nullopt_

* fix merge conflict

* fix merge conflict

* change the output format of C++ backward api

* fix merge conflict

* fix sparse api code auto-gen

* fix eager_gen bug

* fix bug of output is null

* fix bug of conv2d_grad_impl

* fix optional grad

* fix bug of eager-gen double_grad

* fix bug

* fix multiply_double_grad bug

* fix bug of higher order derivative

* fix bug of FillZeroForEmptyGradInput

* remove redundant vector in grad_node

* fix bug of test_deformable_conv_v1_op

* fix bug of test_deformable_conv_v1_op

* some refacotr

* add double yaml

* add inline func

* add yaml

* perfect converage

* [Refactor] refactored eager_gen.py PR #2

* [DoubleGrad PR #1] Decoupled code generation logics for Dygraph ForwardFunctions and GradNodes

* Fixed minor issue

* Adjusted logics of GenerateNodeCreationCodes and GenerateForwardDefinition

* Fixed issues

* Supported higher-order grad node generation

* [DoubleGrad PR #4] Supported higher-order GradNode generation

* [DoubleGrad #4] Bug Fixes to Double Grad Node Generation

* Fixed yaml typo

* Fixed yaml typo

* fixed minor issues

* [DoubleGrad PR #5] Enabled gradient computations for grad_tensors passed to paddle.grad()

* Fixed minor issue

* Fixed CI-Inference issue

* Fixed CI-inference issues

* [DoubleGrad PR #7] paddle.grad() to copy backward graph before backward run

* Fixed minor issues

* Fixed issue with backward graph construction logic

* Fixed implementation issues with backward graph reconstruction

* Fixed unittest issue

* Fixed issues

* [DoubleGrad PR #8] Enabled triple grads for sigmoid and matmul

* Fixed issues with phi kernel

* Added triple grad test case

* Fixed minor issue

* move activation

* fix bugs when run ce

* move activation op

* adjust code format

* fix compile bugs

* fix ci bugs

* code format adjust

* code format adjust2

* activate ci status

* modify according to comment

* move activation kernel

* revert relu6

* reduce add code

* perfect use_phi_functor

* completing func name

* fix bugs when run ci

* fix bugs when run infr

* modifpy infrt get kernel signature

[Phi]Move Relu/Cos/Sin/Tan/Acos/Asin/Atan/Sinh/Cosh/Asinh/Acosh/Atanh kernels in Activation to Phi (#40175)

* move activation op

* adjust code format

* fix compile bugs

* fix ci bugs

* code format adjust

* code format adjust2

* activate ci status

* modify according to comment