Diazo rule to append element before closing tag

Question

I'm trying to find a diazo rule to append a new element in a container before its closing tag. For example:

Case 1
<div class="some-A">
  <div class="some-B">1</div>
  <div class="some-B">2</div>
  <div class="some-B">3</div>
</div>

Case 1 - after rule applied
<div class="some-A">
  <div class="some-B">1</div>
  <div class="some-B">2</div>
  <div class="some-B">3</div>
  <div class="some-B">NEW</div>
</div>

Case 2
<div class="some-A">
</div>

Case 2 - after rule applied
<div class="some-A">
  <div class="some-B">NEW</div>
</div>

I need to have it working for each case - with and without content in container.

None of these are ok:

  <replace css:theme=".some-A">
    <div class="some-A">
      <div class="some-B">NEW</div>
    </div>
  </replace>

because replaces all.

  <before css:theme=".some-A">
    <div class="some-B">NEW</div>
  </before>

because appends before my container.

  <after css:theme=".some-A">
    <div class="some-B">NEW</div>
  </after>

because appends after it.

Answer 1

 <after css:theme-children=".some-A">
    <div class="some-B">NEW</div>
 </after>