* Fix data and reader related api doc

* Fix data and reader related api doc

Review and fix the example code in some reader related API doc.

These APIs are:

Fix existing API example codes:

paddle.fluid.io.PyReader
paddle.fluid.layers.batch
paddle.fluid.layers.data
paddle.fluid.layers.Preprocessor
paddle.fluid.layers.py_reader
paddle.fluid.program_guard

Add new example codes:

paddle.fluid.io.PyReader.decorate_batch_generator
paddle.fluid.io.PyReader.decorate_sample_generator
paddle.fluid.io.PyReader.decorate_sample_list_generator
paddle.fluid.io.PyReader.reset
paddle.fluid.io.PyReader.start

test=develop

* Add changes to API.spec after changing doc.

test=develop

* Add blanks after python example code

test=develop

* Add blank line at py_reader example code

test=develop

* Merge API.spec

test=develop

* Modify reader.py based on reviewer's comment

test=develop

* Modify API.spec after changing doc

test=develop

* Change reader.py based on reviewer's comment

* Modify example code of decorate_sample_generator

test=develop

* Fix example code of PyReader based on reviewer

test=develop

* add use_cuda to inplace pass,test=develop

* add test softmax_with_xe_inplace test,test=develop

* fix potential inplace bug
test=develop

* add more skip vars in mem opt pass,test=develop

* follow comment,test=develop

* follow comments,move duplicate out arg check to program->graph,test=develop

* fix api doc of hash, relu, concat, argmin, argmax, argsoft and all activations funcs with no attrs

test=develop

* refine doc example code

test=develop

* remove >>> in doc example

test=develop

* refine python code block

test=develop

* update API spec

test=develop

test=develop

* remove unused FLAGS_warpctc_dir

test=develop

* remove FLAGS_warpctc_dir

test=develop

* add attr axis infershape. test=develop

* add CUDA kernel. test=develop

* fix unittest. test=develop

* fix unittest for soft_label. test=develop

* fix fp16 unittest. test=develop

* remove comment code. test=develop

* refine test for axis. test=develop

* add python api. test=develop

* fix doc. test=develop

* fix fp16 unittest. test=develop

* fix ngraph test. test=develop

* fix ENFORCE for test_imperative_transformer. test=develop

* fit for ngraph test. test=develop

* fix after rebase develop. test=develop

* fix doc. test=develop

* fix API.spec. test=develop

* fix test_layers. test=develop

* fix format. test=develop

integer', test=develop

* Add MovingAverageAbsMaxScale operator which is only used for calculating the quantization scale.

* test=develop

* change the output into inplace. test=develop

* Revert "test=develop"

This reverts commit 696cf62699ba1e1c98f61f7345ac7060010eb29a.

* Revert "change the output into inplace. test=develop"

This reverts commit a19acd20f07eee82622701a3015e6e9c073a5e0b.

* test=develop.

* update the MovingAverageAbsMaxScaleOp test. test=develop

* optimize sum op

fuse multi eigen kernel calls into one cuda kernel.
refine code

test=develop.
Signed-off-by: Nzhaoyuchen <zhaoyuchen01@baidu.com>

* Refine code.

test=develop
Signed-off-by: Nzhaoyuchen <zhaoyuchen01@baidu.com>

* Refine code according to comments.

test=develop

* refine code

delete sum_op_gpu.h
test=develop

* Fix test error.

test=develop
Signed-off-by: Nzhaoyuchen <zhaoyuchen01@baidu.com>

* refine code in format.

test=develop.

* refine code

test=develop
Signed-off-by: Nzhaoyuchen <zhaoyuchen01@baidu.com>

* refine code

test=develop
Signed-off-by: Nzhaoyuchen <zhaoyuchen01@baidu.com>

* cherry-pick commit from 88770542

* cherry-pick commit from 3f0b97df

* cherry-pick from 16691:Anakin subgraph support yolo_v3 and faster-rcnn

(cherry picked from commit 8643dbc2)

* Cherry-Pick from 16662 : Anakin subgraph cpu support

(cherry picked from commit 7ad182e1)

* Cherry-pick from 1662, 16797.. : add anakin int8 support

(cherry picked from commit e14ab180)

* Cherry-pick from 16813 : change singleton to graph RegistBlock
test=release/1.4

(cherry picked from commit 4b9fa423)

* Cherry Pick : 16837 Support ShuffleNet and MobileNet-v2

Support ShuffleNet and MobileNet-v2, test=release/1.4

(cherry picked from commit a6fb066f)

* Cherry-pick : anakin subgraph add opt config layout argument #16846
test=release/1.4

(cherry picked from commit 8121b3ec)

* 1. add shuffle_channel_detect

(cherry picked from commit 6efdea89)

* update shuffle_channel op convert, test=release/1.4

(cherry picked from commit e4726a06)

* Modify symbol export rules

test=develop

test=develop

* refine api comment, test=develop

* call SetNumThreads everytime to avoid missing omp thread setting

resolve #17153
test=develop

* add paddle_num_threads into config for test_analyzer_pyramid_dnn

resolve #17153
test=develop

* fix unexecutable API comments, test=develop

* add API.spec,test=develop

* fix distribute fpn proposals, test=develop

* fix profiler and name_scope API examples

test=develop

* update API.spec

test=develop

* fix tensor_py,test=develop

* change class name,test=develop

* add use_cuda to inplace pass,test=develop

* add test softmax_with_xe_inplace test,test=develop

test=develop

* enhance_concat, test=develop

* remove unnecessary set_devices

* remove async executor python api
test=develop

* remove test_async_executor.py
add executor train_from_dataset demo
test=develop

* fix import bug
test=develop

* fix mem leak when converting Tensor to numpy array
test=develop

* remove unused unittest,test=develop

* follow comments, test=develop

* fix dygraph bug,test=develop

test=develop

* fix bn fuse vardesc and add model saver

test=develop

* unify save model in test helper

test=develop

* fix mkdir on windows

test=develop

* remove magic number use bn bias var desc

test=develop

* fix op graph view
test=develop

* rewrite inplace pass and fix reference count pass bug
test=develop

* fix unittest failed
test=develop

* follow comments, test=develop

* polish the label_smooth

test=develop

* polish code

test=develop

resolve #17147
test=develop

cvm without LoD.

* refine_dropout_mem,test=develop

* # This is a combination of 14 commits.
# The first commit's message is:
remove ut test_dist_word2vec in mac ci, will fix it in private, test=develop (#17066)

# This is the 2nd commit message:

Fleet unify distributed training (#16791)

* implement distributed transpiler with fleet
# This is the 3rd commit message:

ParallelDyGraph with GPU collective mode (#16827)

implement dygraph.parallel.DataParallel to hook reduce op.

# This is the 4th commit message:

Init mixed precision training interface (#16856)

* Init mixed precision training interface

* Add fp16 test script

test=develop

* All initializers support float16

test=develop

* Code cleanup & add more code annotations

test=develop

* Update API spec

test=develop

* Add usage example in doc

test=develop

# This is the 5th commit message:

fix reference_count_pass,test=develop (#17060)

test=develop
# This is the 6th commit message:

Speedup roi_perspective_transform op by caching the information of linear interpolation in forward (#17090)

* Cache the information of linear interpolation in forward and use it in backward.
test=develop

* Fix cuda kernel.
test=develop

# This is the 7th commit message:

remove unnecessary prepare_data (#17080)

test=develop
# This is the 8th commit message:

fix interpolate cu. test=develop (#17101)

# This is the 9th commit message:

test=develop, double backward leaky_relu (#17067)

backward of backward: leaky_relu
# This is the 10th commit message:

fix fuse optimizer ops (#17102)

test=develop
# This is the 11th commit message:

truncated_gaussian_random supported in distributed training, test=develop (#17091)

# This is the 12th commit message:

 Detailed coordinate description for yolov3 loss (#17007)

* Detailed coordinate description for yolov3 loss

test=develop

* modified api.spec

test=develop

* modified loss name

* fix api.spec

test=develop

* polish description

test=develop

* modified api.spec

test=develop

# This is the 13th commit message:

fix test_weight_decay (#17109)

test=develop
# This is the 14th commit message:

Path flag (#17105)

* fix python/paddle/fluid/__init__.py detecting problems

1. Use CudnnWorkspaceHandle in exhaustive search of conv_cudnn.
2. For Ops using CudnnWorkspaceHandle in exhaustive search, release their GPU memory after exhaustive search.

test=develop

* Detailed coordinate description for yolov3 loss

test=develop

* modified api.spec

test=develop

* modified loss name

* fix api.spec

test=develop

* polish description

test=develop

* modified api.spec

test=develop

test=develop

backward of backward: leaky_relu