add unit-test for chinese_ner

Fix generator not closed when iteration end bug

* Add pad2d op.

* Add unitest and python api.

* Fix cuda op kernel.

* Fix python api.

* Fix python api.

* Update API.spec.

* Fix python api

support op_namescope for better debugging

Fix bug when loss@GRAD is reused.

fix mkldnn include format

* fix dist train reduce mode

* fix previous fix

use fast RunPrepareContext for inference

fix_book_doc

* Add unit test for rpn_target_assign API.

refine memory usage calc

* Add generate_proposal_labels for Faster-RCNN.

Wrap unsqueeze & squeeze ops

* Enhance the function of fused_elementwise_activation_op

* enhance unit test

* Clean Code And Add Doc

* Add compound functors

* Fix doc and enhance unit test

* define Dx and Dy for d_binary_func

* add mul_scale

* add mul_scale

* add elementwise_mul

* code refine

* code refine

* add doc

* add  AsIntermediate

* add test for dist and memopt

* update transformer too

add python api for sampling_id op

fix graph_to_program_test to be platform-independent

* fix dist transpile with memopt

* update api.spec

* polish dist transpile api

* update apispec

* update apispec