2. fix bug in backward.py: using fill_constant instead of fill_constant_batch_size_like
3. fix bug in ExpandGradOp.

test=develop

* modified group_norm's unittest for pass statement, test=develop

* fix group_norm's bug: scale or bias is None which causes segmentation fault, test=develop

* Fix the assign data check. test=develop

* Fix test_assign_op.py. test=develop

* disable nccl test

* Update version.

* fix term core only

* fix transpiler error

* fix protobuf memory leak (#11177)

fix protobuf memory leak

* "change eigen mirror"

* refine en doc sequence enum pad expand mask d2s

* refine seq enum expand mask pad test=develop, test=document_fix

* remove cn char test=document_fix

* spec test=document_fix

* code style test=document_fix

* test=document_fix

* test=document_fix

* test=document_fix

* test=document_fix

* test=document_fix

* test=document_fix

* fix en docs of Layer and guard
test=document_fix, test=develop

* fix en docs of Layer and guard
test=document_fix, test=develop

* minor fix
test=document_fix, test=develop

* minor fix
test=document_fix, test=develop

* fix api.spec
test=document_fix, test=develop

* fix api.spec
test=document_fix, test=develop

* fix docs
test=document_fix, test=develop

* fix docs
test=document_fix, test=develop

* fix docs
test=document_fix, test=develop

* fix api.spec
test=document_fix, test=develop

* fix api.spec
test=document_fix, test=develop

* add forward doc
test=document_fix, test=develop

* add "s" for parameters
test=document_fix, test=develop

* update data feeder API sample, fluid.layers.data => fluid.data

* update API.spec

* fix doc of default_main_program, multiprocess_reader

* update API.spec

* fix comment

* Refine the documentation of sums.

* Remove Chinese comments and update API.spec.

* Refine the description of input argument.

* Update API.spec.
test=develop
test=document_fix

Add API 'fluid.requird_version(min_version, max_version=None)' to check if the installed PaddlePaddle version is satisfied, test=develop (#20263)

添加API：fluid.version_required(min_version, max_version=None)，用于检查已安装的PaddlePaddle版本是否符合要求
无返回值，如果已安装的版本不在区间[min_version, max_version]，则抛出异常。
例：安装的版本为1.6.0，调用：fluid.require_version('1.5.0', '1.5.1')，则抛出异常：
Exception: VersionError: PaddlePaddle version in [1.5.0, 1.5.1] required, but 1.6.0 installed.

* Refine create_array api en doc

test=develop
test=document_fix


* Fix api doc example bug and polish square

test=develop
test=document_fix


* Refine comment

test=develop
test=document_fix


* refine API.spec

test=develop
test=document_fix

refine the en api doc of ones, zeros, reverse, assign, increment, hsigmoid and create_py_reader_by_data ops (#20343)

* refine the en api doc of ones, zeros, reverse, increment, hsigmoid and create_py_reader_by_data ops
test=develop, test=document_preview, test=document_fix

* refine eng doc for hsigmoid and create_py_reader_by_data ops
test=develop, test=document_preview, test=document_fix

* update API.spec
test=document_fix

* Fix the parameter name axis of reverse op in eng doc
test=develop, test=document_fix

* Update API.spec
test=develop, test=document_fix

* Refine eng doc of zeros, ones, reverse and assign op
test=develop, test=document_fix

* Update API.spec for assign, ones, zeros and reverse
test=develop, test=document_fix

* Fix data type of reverse op in eng doc
test=develop, test=document_fix

* Update API.spec for reverse op
test=develop, test=document_fix

* test=develop, add unittest  of seed failed work

* test=develop, add unittest  of seed failed work

* support reshape doubel grad, test=develop

* fix reshape double grad, pass converage, test=develop

* fix review, test=develop

* fix_norm_model_average_bug

* test=develop

* refine comment test=develop

* refine comment test=develop

* refine eng doc for hard_sigmoid op
test=develop
test=document_fix

* refine the description of hard_sigmoid
 test=develop
test=document_fix

* update API.spec
test=document_fix

* Refine the decription of parameters of HardSigmoid op
test=develop, test=document_fix

* Update API.spec for hard_sigmoid op
test=develop, test=document_fix

* enhance embedding error message test=develop

* enforce .h error test=develop

* fix unittest code test=develop

* Fix fp16 dtype in embedding test=develop

* add import warnings test=develop

* Fix the error message of assign op
test=develop

* Refine input type checking for assign op
test=develop

* Refine unittest of assign op
test=develop

* add input type and dtype check, enhance shape error message for concat_op
test=develop

* enhance shape check
test=develop

* improve coverage

test=develop

* fix APIs: relu, relu6, hash

test=develop
test=document_fix

* fix relu6 doc

test=develop
test=document_fix

* fix API.spec

test=develop
test=document_fix

* add description link for hash

test=develop
test=document_fix

* improve data feeder related API

* Refine topk stack squeeze api en doc

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

* Refine api en doc

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

* refine api.spec and returns

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

* add input type and dtype check for accuracy_op

* add input type and dtype check for accuracy_op

* modify python error on accuracy_op,add test=develop

* modify details on accuracy_op, test=develop

* test float16, test=develop

* add warning, test=develop

test=document_fix

* enhance mul_op input error message test=develop

fix sign op input error check
test=develop

* Fix api docs. test=document-fix

* Fix en docs. test=develop

* Fix the doc of dynamic_gru. test=document_fix

* Update API.spec. test=document_fix

* Fix codestyle test=develop, test=document_fix

* fix APIs: cast, concat, tensor_array_to_tensor, argmin, argmax, argsort

test=develop
test=document_fix

* fix API:cos, exp, ceil, elu, brelu English doc
test=develop
test=document_fix

* refine 13 en doc

* fix Print, is_empty, read_file test=document_fix

* fix the precise roi poop op test=develop
add roi backward implementation, fix the output-channel

* Refine the main comment of DynamicRNN.

* Refine the documentation of DynamicRNN's step_input function.

* Refine the documentation of DynamicRNN's static_input function.

* Refine the documentation of DynamicRNN's block function.

* Refine the documentation of DynamicRNN's memory function.

* Refine the documentation of DynamicRNN's update_memory and output function.

* Refine the code format and remove the method list.

* Refine the documentation of DynamicRNN's __call__ function.
test=develop
test=document_fix

* Minor modification.
test=develop
test=document_fix

* Fix some typo.

* Update API.spec.
test=develop
test=document_fix

* Refine the English according to the comments.

* Update API.spec.
test=develop
test=document_fix

* Fix some typo.

* Update API.spec.