test=develop

* Remove Desc in Forward Pass

* Refactor VarBase

* Add dbg info

* Only check type in imperative mode

* Polish code and support optimizer

test=develop

* Fix stop gradient problem in PyLayer

test=develop

test=develop

* fix recordio on win
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* test=develop

* test=develop

* fix code style
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* test=develop

test=develop

test=develop

* add parallel graph dist test=develop

* update test=develop

* update style test=develop

* add parallel graph dist test=develop

* update test=develop

* update style test=develop

* Enable INT8 ReQuantize OP
test=develop

* Clean code
test=develop

* Add comments
test=develop

* Revert "Clean code"
test=develop

This reverts commit a7a49b8a.

* Modify requantize op test
test=develop

* fix requantize UT by moving public function to public test file.
test=develop

* Fix test fail due to file address change.
test=develop

* Change file address for requantize op.
test=develop

test=develop

* test=develop, reconstruct layer helper to fit imperative usage

* test=develop, fix import error on py35

* test=develop, fix rnn gradient error

* test=develop, delete test use code

* test=develop, remove helper from imperative usage

* test=develop, fix test_base_layer using new helper

* test=develop, reconstruct layerhelper for imperative mode

* test=develop, reconstruct layerhelper for imperative mode

* test=develop, fix bug

* test=develop, fix test failed bug

* test=develop, fix test failed bug

* test=develop, fix test failed bug

* test=develop, fix bug

* test=develop, polish code

* add ir memory optimize test case for IfElse op, test=develop

* fix some unitttest failure by force using the python memory_optimize, test=develop

* tweak comments, test=develop

* fix unittest, test=develop

* fix unittest, test=develop

test=develop

* MKLDNN: Add UT for conv_transpose_mkldnn op.
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* MKLDNN: Add fuse_bias check UT for conv_transpose_mkldnn op.
test=develop

* test=develop, reconstruct layer helper to fit imperative usage

* test=develop, fix import error on py35

* test=develop, fix rnn gradient error

* test=develop, delete test use code

* test=develop, remove helper from imperative usage

* test=develop, fix test_base_layer using new helper

* test=develop, reconstruct layerhelper for imperative mode

* test=develop, reconstruct layerhelper for imperative mode

* test=develop, fix bug

* test=develop, fix test failed bug

* test=develop, fix test failed bug

* test=develop, fix test failed bug

* test=develop, fix bug

* test=develop, polish code

test=develop

test=develop

* add ir memory optimize test case for IfElse op, test=develop

* fix some unitttest failure by force using the python memory_optimize, test=develop

* tweak comments, test=develop

* fix unittest, test=develop

* fix unittest, test=develop

test=develop

* MKLDNN: Add UT for conv_transpose_mkldnn op.
test=develop

* MKLDNN: Add fuse_bias check UT for conv_transpose_mkldnn op.
test=develop