* fix recurrent bug
test=develop

* support dlpack to tensor and implement python interface test=develop

* add unittest for _to_dlpack and from_dlpack test=develop

test=develop

* add expand_as op, test=develop

* add expand_as op,test=develop

* add expand_as op,test=develop

* add nn.py, test=develop

* delele paddle_enforce, test=develop

* refine py_reader exit, test=develop

* fix multiprocess_reader exception unittest, test=develop

* increase code coverage for legacy fluid.layers.py_reader, test=develop

* Fix docs of gru_unit and dynamic_gru.

Fix basic_gru in rnn_impl.py.

Add error messages for param_attr setting in layer_norm api.

Add int64 dtype for expand.

test=develop

* Reopen unit-tests of basic_gru/basic_lstm in rnn_impl.py.
test=develop

* Add unit test for layer_norm api.
test=develop

* Remove the deprecated gru doc fix. test=develop

* Fix basic_gru test coverage. test=develop

* Update API.spec. test=develop

* Update API.spec. test=develop

* Fix test_basic_gru coverage test. test=develop

* Update test_basic_gru in test_layers to use fluid.data
test=develop

* Update test_basic_gru for coverage. test=develop

* Refine error message of transpose.
* Fix transpose, multiplex, unsqueeze, unstack. test=develop, test=document_preview, test=document_fix

* fix the error message of zeros op
test=develop

* Fix unittest of zeros op
test=develop

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

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.

* 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

* 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

* 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

* enhance mul_op input error message test=develop

fix sign op input error check
test=develop

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

* 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

test=develop

* fix expand bug test=develop

* fix style test=develop

* fix style test=develop

* fix style test=develop

* fix style test=develop

* 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

enhance shape error messages for reshape op.
test=develop

* 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

* Add detailed error messages for nce layer

test=develop

* Fix some problems

test=develop

* Fix unit test coverage

test=develop

test=develop

* elu input check
test=develop

* test=develop

* rm unused ckpt and sort ckpt

* use max op idx to sort, test=develop

* remove unsed code,test=develop

* add testcase, test_develop

* modify test case, test=develop

Refine error message for new data API