* Modify lod_tensor.md and nn.py

* Modify control_flow.py doc

* undo change in lod_tensor.md

* add lod_tensor util and modify pybind

* refind pybind LoDTensor API and modify LoDTensor and DataFeeder test

* fix test error

* fix detection map op test

* fix reorder_lod_tensor test

* fix seq_concat_op

* fix chunk evel op test

* fix target assign op

* fix warp ctc op

* address comments step 1: reverse reset_lod op

* step 2: modify op test

* add warning message

* remove has_valid_lod

* add back has_valid_lod

* address comments

* add exception catching trial

* Implement a bilinear initializer for transposed convolution.

* Update some error message.

* Update some doc about layers' API.

* Fix format.

* Fix example bug in random_data_generator.

* Fix example bug in dropout.

* Follow comments and some small fix for some examples.

* fix mac build error

* enhance memory optimize transpiler to let users set to some skip opt set of variables