Question About Group Example

[vip30]

Here is the link
https://github.com/kazupon/vue-validator/blob/dev/examples/group/index.html

vue & vue-validator version

2.1.0 , 3.0.0-alpha.2

I would like to ask about if I want to trigger the whole form valiidate before submit (or in submit).
What should I do?
In the group example, I would like to have each input contains value before submit. But now, it can be submit with empty string.
In the previous version, there is a function this.$validate(true, function(){})
In 3.0, is there any similar function?