* refactor eager flags

* fix flags error when we switch from eager to dygraph

* fix ci problem

* fix ci

* fix ci

* merge develop and fix code style

* merge develop and fix code style

* fix op test error

* fix op test error

* fix op test error

* fix op test error

* fix op test error

* merge develop

* fix warning error , test=document_fix

* fix warning error , test=document_fix

* fix warning error , test=document_fix

* fix warning error , test=document_fix

* fix warning error , test=document_fix

* fix warning error , test=document_fix

* fix warning error , test=document_fix

* import sequence_* API to new namespace

* fix typos, remove alias marking

* update sample code

* fix sample code

* fix docstring for sequence_mask

* upgrade comment string to raw string

* fix string in

* fix string with ' '

* revert update on comments

* upgrade only necessary

* fix sample code checker

* fix comments with '''

* Fix wrong out dtype from helper.input_dtype

* add unittest

* remove disable_static in op_test

* fix param name typo

add fp64 support in sequence_pool, test=develop

API/OP(sequence_first_step, sequence_last_step, sequence_mask, beam_search, beam_search_decode) error message enhancement (#24590)

* API/OP(sequence_expand_as) error message enhancement.
test=develop
Co-authored-by: NFrostML <380185688@qq.com>

* Format error message for ops, test=develop

* Fix check in sequence_expand, test=develop

* polish some sl api error message, test=develop

* polish python input check of stride slice, test=develop

* fix unittest bugs, test=develop

* test=develop

* solve the conflict of ops with the same name. test=develop

This reverts commit abe3e690.
test=develop

* solve the conflict of ops with the same name. test=develop

* split some APIs from nn.py to rnn.py

* split some APIs from nn.py to sequence_lod.py

test=develop

* fix unit-test bug

test=develop

* fix test_layers unit-test bug

test=develop