title: Uncheck all treeview checkboxes
body: <p>I have a <code>v-treeview</code> component (Vuetify 2.6.7)</p>
  <pre><code>&lt;v-treeview
              class=&quot;location-tree&quot;
              v-model=&quot;location_tree&quot;
              ref=&quot;location_tree&quot;
              :search=&quot;location_search&quot;
              selectable
              dense=true
              open-on-click=true
              expand-icon=&quot;$plus&quot;
              selected-color=&quot;success&quot;
              :items=&quot;locations&quot;
              selection-type=&quot;all&quot;
              transition=true
              @input=&quot;location_tree_update&quot;
  &gt;&lt;/v-treeview&gt;
  </code></pre>
  <p>How can I uncheck <strong>all checkboxes</strong> with a some button click?</p>