test=develop

test=develop

test=develop

test=develop

* Add roi perspective transform.

* Add roi_perspective_transform_op.

* Fix code style.

* Add python api and fix doc.

* Fix API.spec

* Fix python api.

* Fix API.spec

* Move src to detection.

Sequence Scatter Op

* Add python api for expand op.

* Fix unitest.

* Remove 'out' from arguments and fix code style.

* fix API.spec

* Fix API

* Fix unitest

* add ignore index

* update api.spec

* enhance softmax_with_cross_entropy

* Add pad2d op.

* Add unitest and python api.

* Fix cuda op kernel.

* Fix python api.

* Fix python api.

* Update API.spec.

* Fix python api

* Fix scatter_op python API and remove inconsistency between implementation and doc

* API spec change

* Change as review comment

* Add three modes for prelu_op.

Add flatten op interface and enhance APIs about detection to support variable-length image. (#12422)

* add flatten api&enhance detection api

* unify shape_op data type

* update API.spec

* api clean

* update API.spec

* expose rank_loss python api

* change im2sequence for ctc batch inference

* Update im2sequence_op.cc

* change im2sequence for ctc batch inference

* update

* change PR by comment

* fix ocr test error

* fix test_im2sequence

* modify the old name to standard name

* fix test_layers failed

* Fix mean iou op.

* Fix crop layer test.

* Fix unitest

* fix unitest.

* Add normalization operator.
1. Refine the raw norm_op and let it more general to support to normalize Tensor along any axis.
2. There is a bug in l2_normalize API, which lacks sqrt after `reduce_sum`.
3. Use norm_op to refine the l2_normalize API.
4. Fix bug in test_normalization_wrapper.py.

* Expose maxout API.

* Fix code style.

* Auto generate python api for polygon_box_transform op.

* Add unitest.