* Fix examples of fluid.layers.sums.
test=document_preview

* Correct the example of DynamicRNN and its functions.
test=develop

* Add 'import paddle.fluid as fluid' to examples.
test=develop

* Update API.spec.
test=develop

* Add space lines.
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* Update the API.spec.
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* Add api doc code examples

add or fix topk, squeeze, stack, StaticRNN,
StaticRNN memory in doc

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

* Add squeeze md5.

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

* Add import package

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

* test=develop
update API.spec with hash, resolve conflict

* remove unused parameter

* enable recurrent op test=develop

* wip allreduce in op

* wip

* wip

* wip

* wip adding test

* wip for conflict with mp mode

* fix tests test=develop

* fix cpu build test=develop

* fix travis clang format test=develop

* fix cpu build test=develop

* update api.spec test=develop

* delete comment test=develop

* fix cpplint test=develop

* fix test=develop

* follow comment test=develop

* add file test=develop

* fix build test=develop

* update test=develop

* to be compatible with sync_bn, and fix mp mode in develop test=develop

* Make step_input support custom lod level.
test=develop

* Fix API.spec
test=develop

* Fix API.spec.
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* Fix API.spec
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* Add default value in document of step_input.
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* Fix document.
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* Fix API.spec
test=develop

* remove the ignored from is_empty and less_than test=develop

* fix api spec test=develop

* fix the api spec test=develop

* test=develop

* remove the ignored from is_empty and less_than test=develop

* fix api spec test=develop

* fix the api spec test=develop

* test=develop

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

* Correct the comment in control_flow.py.

* Correct the argument list of ops.
test=develop

* Update API.spec.
test=develop

* Skip op_callstack attr for all op apis.
test=develop

* Remove use_mkldnn and is_test from python api.
test=develop

* Remove use_mkldnn and is_test from op_proto_maker and hard-coding them in python when generating doc string.
test=develop

test=develop

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* remove unnecessary var_and_op
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* fix _init_zero_idx_
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avoid the default one that usually overwrites manually set ones

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* hide program APIs

* fix merge error

* update

* Polish PrintOp

* Polish PrintOp

* Polish PrintOp

* Refine test_print_op

* add is_test for while_op

* Change API

* Fix bug in conditional_block_op.
* Fix bug and add comments.
* Rename arguments.

* Hidden APIs for While, StaticRNN, ParallelDo.

* Hiden some LoDTensor ralatted ops' Python wrapper.

* remove block api

* remove clone_variable

* hide block inner apis

* update

* fix tests

* Modify lod_tensor.md and nn.py

* Modify control_flow.py doc

* undo change in lod_tensor.md