Merge pull request !1402 from zongha/master

Merge pull request !1160 from wangqiuliang/add-backward-hook-in-pynative-mode

Merge pull request !1397 from liubuyu/master

Merge pull request !1403 from zhaozhenlong/fix-issues-scatter-max-comment

Merge pull request !1295 from Margaret_wangrui/new-parameter

Merge pull request !1339 from JichenZhao/layernorm_mean_var_shape

add some unittest for summary operator

support ScalarSummary to record number type

Merge pull request !1363 from zhangbuxue/Not_support_mixed_tensor_as_index_for_tensor_getitem_and_setitem

Merge pull request !1366 from jiangjinsheng/issue_invert

Merge pull request !1333 from jiangjinsheng/vm_erfc

Merge pull request !1344 from jiangjinsheng/issue_batchnorm_grad

Merge pull request !1338 from liuxiao/UnsortedSegmentMinD-UnsortedSegmentMin

Merge pull request !1133 from zhangbuxue/support_tensor_get_value_by_tensor_index

support tensor set value by tensor index

Merge pull request !1302 from lihongkang/master

Merge pull request !1312 from jiangjinsheng/vm_erfc

Merge pull request !1304 from amongo/AddCheckForControlDepend

Merge pull request !1223 from zhouneng/add_examples_for_ops

Merge pull request !1292 from jiangjinsheng/issue_broadcast

Merge pull request !1282 from jiangjinsheng/vm_prelu

Merge pull request !1258 from jiangjinsheng/issue_lstm_dropout

Merge pull request !1125 from jiangjinsheng/space_to_depth

Merge pull request !1262 from wanghua/master

Merge pull request !1111 from jiangjinsheng/vm_pack

Merge pull request !1242 from jiangjinsheng/vm_arg_max