pyang -f sample-xml-skeleton -p draft-yangs --sample-xml-skeleton-doctype=config -V --sample-xml-skeleton-defaults -o ietf-udp-notif-example.xml /Users/ahuangfeng/.pyenv/versions/3.9.5/share/yang/modules/ietf/ietf-subscribed-notifications.yang ietf-udp-notif.yang