From: @pengyongrong
Reviewed-by: @ddwsky,@zhanghaibo5
Signed-off-by: @ddwsky

From: @dinglongwei
Reviewed-by: @liangchenghui,@c_34
Signed-off-by: @liangchenghui,@c_34

From: @cjh9368
Reviewed-by: @hangangqiang,@zhanghaibo5
Signed-off-by: @hangangqiang

From: @mengyuanli
Reviewed-by: @hangangqiang,@zhanghaibo5
Signed-off-by: @hangangqiang

From: @TFbunny
Reviewed-by: @robingrosman,@tom__chen
Signed-off-by: @robingrosman

From: @lixiachen
Reviewed-by: 
Signed-off-by:

From: @mengyuanli
Reviewed-by: @hangangqiang,@zhanghaibo5
Signed-off-by: @hangangqiang

From: @lx0095
Reviewed-by: @zhanghaibo5,@zhang_xue_tong
Signed-off-by: @zhang_xue_tong

From: @ling_qiao_min
Reviewed-by: @hangangqiang,@zhanghaibo5
Signed-off-by: @hangangqiang

From: @Somnus2020
Reviewed-by: @wangnan39
Signed-off-by:

From: @mengyuanli
Reviewed-by: @hangangqiang,@zhanghaibo5
Signed-off-by: @hangangqiang

From: @zhangbuxue
Reviewed-by: 
Signed-off-by:

From: @wyann22
Reviewed-by: @anyrenwei,@ckey_dou
Signed-off-by: @ckey_dou

From: @dayschan
Reviewed-by: @gaoxiong1,@ckey_dou
Signed-off-by: @ckey_dou

From: @shenwei41
Reviewed-by: @liucunwei,@heleiwang
Signed-off-by: @liucunwei

From: @louisncu
Reviewed-by: @hangangqiang,@HilbertDavid
Signed-off-by: @hangangqiang

From: @xulei2020
Reviewed-by: @pandoublefeng,@liucunwei
Signed-off-by: @pandoublefeng

From: @luoyang42
Reviewed-by: 
Signed-off-by:

From: @fangzehua
Reviewed-by: 
Signed-off-by:

From: @qujianwei
Reviewed-by: @c_34,@liangchenghui
Signed-off-by: @c_34

From: @yangruoqi713
Reviewed-by: @zhanghaibo5,@zhang_xue_tong
Signed-off-by: @zhang_xue_tong

From: @zhangbuxue
Reviewed-by: 
Signed-off-by:

From: @zhangxinfeng3
Reviewed-by: @ckey_dou,@wang_zi_dong
Signed-off-by: @wang_zi_dong

From: @zhengjun10
Reviewed-by: 
Signed-off-by:

From: @jiangzg001
Reviewed-by: @liangchenghui,@c_34
Signed-off-by: @liangchenghui

From: @wanyiming
Reviewed-by: 
Signed-off-by:

From: @wangrao124
Reviewed-by: @wuxuejian,@kisnwang
Signed-off-by: @wuxuejian

From: @yepei6
Reviewed-by: 
Signed-off-by:

From: @changzherui
Reviewed-by: 
Signed-off-by:

From: @wangrao124
Reviewed-by: @liangchenghui,@zhunaipan
Signed-off-by: @liangchenghui

From: @ginfung
Reviewed-by: 
Signed-off-by:

From: @ling_qiao_min
Reviewed-by: 
Signed-off-by:

1. description of num_shard in datasets.py
2. add param validation for sampler
3. add description for add_child in sampler.py

fix c++ ut compilation failed of Asan bug