Multiple indeterminate checkbox not working

I have got the way to do indeterminate checkbox on here

But I'm looking for multiple indeterminate checkbox like here

<div class="container">
  <ul>
    <li>
      <input type="checkbox" class="option"><label for="option"> Electronics1</label>
      <ul>
        <li><label><input type="checkbox" class="subOption"> Laptops</label></li>
        <li><label><input type="checkbox" class="subOption"> TVs</label></li>
        <li><label><input type="checkbox" class="subOption"> Microphones</label></li>
      </ul>
    </li>
    <li>
      <input type="checkbox" class="option"><label for="option"> Electronics2</label>
      <ul>
        <li><label><input type="checkbox" class="subOption"> Laptops</label></li>
        <li><label><input type="checkbox" class="subOption"> TVs</label></li>
        <li><label><input type="checkbox" class="subOption"> Microphones</label></li>
      </ul>
    </li>
  </ul>
</div>

Please help me to know better way to handle multiple nodes.