* Add seq2seq api related code (#19820)

* fix expand bug  (#20340)

* fix expand bug test=develop

* fix style test=develop

* fix style test=develop

* fix style test=develop

* fix style test=develop

* Fix the assign data check (#20564)

* Fix the assign data check. test=develop

* Fix test_assign_op.py. test=develop

* Update API.spec

Refine error message of transpose. fix en doc about unsqueeze, unstack, transpose, multiplex. test=develop, test=document_preview, test=document_fix (#20594)

* Add input check and refine error message

* Refine test case and comments

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

* fix error message for elementwise_add/mul;test=develop

* edit error message;test=develop

* add unittest  of seed failed work

* tadd unittest  of seed failed work

* fix the parameter seed failed to work

fix sign op input error check
test=release/1.6

Fix api doc example bug and polish square doc (#20491)

test=develop
test=document_fix

* Refine topk stack squeeze api en doc

test=develop
test=document_fix

* refine api.spec and returns

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

* fix doc,  updates API documents of uniform_random and  uniform_random_batch_size_like (#20316)

*  fix doc, updates document of sequence_softmax, sequence_scatter, sequence_unpad (#20269)

Refine the en api doc of ones, zeros, reverse, assign, increment, hsigmoid and create_py_reader_by_data ops (#20343) (#20563)

test=develop, test=release/1.6, test=document_fix

* 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, test=release/1.6, test=document_fix

* 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

* fix elementwise floordiv mod; test=develop

* restore nn.py; test=release/1.6

* change floordiv, mod  doc; test=release/1.6

* 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

[cherry-pick] fix Attr(scale)'s bug for image_resize and modified unittest, test=release/1.6 (#19983) (#20460)

[cherry-pick] add input type and dtype check for  elu_op (#20106) fix GradientClipByNorm english doc (#20224) (#20457)

* fix GradientClipByNorm english doc (#20224)

* fix GradientClipByNorm english doc
test=develop
test=document_fix

* add input type and dtype check for  elu_op (#20106)

* elu input check
test=develop

* test=develop

* Polish En doc for some APIs
* Update some comments and API.spec

test=release/1.6

* Add fp16 in input.dtype check test=develop

* Add warning of fp16 in CPU test=develop

* add unittest code for fp16 test=develop

* fix float16 list error test=develop

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

* 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

* cherry-pick fix prroi op test=develop test=release/1.6

cherry pick 91693b9c and resolve conflict in API.spec, test=document_fix (#20477)

modify en api doc

- leaky_relu
- less_than 
- log
- logical_and
- logical_or
- logical_xor
- logical_not

* fix some en doc test=develop test=document_fix

* fix new fluid.data API.spec test=develop test=document_fix

* fix typo test=develop, test=document_fix

* fix typo test=develop test=document_fix

* fix typo test=develop test=document_fix

* fix test=develop test=document_fix

* fix according review test=develop test=document_fix

* fix review test=develop test=document_fix

* fix according review advice test=develop test=document_fix

* fix the doc  test=develop test=document_fix

* fix API.spec test=develop test=document_fix

refine en api doc of [shape, scale, split, selu, soft_relu, scatter], test=develop, test=document_fix (#20264) (#20458)

* add new save load interface; test=develop

* add new save interface; test=develop

* add save load interface ;

* fix save load error;

* fix dygraph set dict bug;

* add save load unit test; test=develop

* fix test_imperative_optimizer bug; test=develop

* fix unitest optimizer bug; test=develop

* fix code coverage; test=develop

* fix converage; test=develop

* add document for apis; test=develop

* fix unitest error; test=develop

* fix save load unit test error; test=develop

* fix error message; test=develop

* change set_parameter set_optimizer to save_dygraph; test=develop

* add load_graph check; test=develop

* fix api spec; test=develop

Fix the api input type and data dtype check in the op of sign
test=release/1.6

* fix the reduce api en doc test=document_fix test=develop

* fix the fluid.data test=develop test=document_fix

* fix the API.spec test=develop test=document_fix

* fix according the review test=develop test=document_fix

* fix the confilict test=develop test=document_fix

update the api en_doc of has_inf, has_nan, cumsum, double_buffer and mul

* add api check in fc test=develop

* enforce shape error info of sum op test=develop

* fix spelling test=develop

* print x_dims info test=develop

* enhance shape error info test=develop

test=release/1.6, test=document_fix

test=release/1.6, test=document_fix