@momentum-ui/react-collaboration/scss/components/checkbox/examples/indeterminate.html

Cisco Momentum UI Framework for React Collaboration Applications

 <div class="md-input-container md-checkbox">
   <input id="indeterminate-checkbox" type="checkbox" class="md-input md-checkbox__input indeterminate">
   <label class="md-checkbox__label" for="indeterminate-checkbox">
     <span>Indeterminate Checkbox</span>
   </label>
 </div>