vue component - What is v-mdl in vue.js?

Question

What is v-mdl (not v-model) in vue.js ? I have started working on a project and I am seeing v-mdl in some places as follows:

<div :id="id" v-mdl class="item" @click="toggle()">

Answer 1

v-mdl is probably an custom directive created in somewhere else.

You can find documentation about custom directives here: https://vuejs.org/v2/guide/custom-directive.html