msubsup-09.test

<<< native
[ ESubsup
    (EIdentifier "M")
    (ESubsup (EIdentifier "B") (ENumber "4") (ENumber "3"))
    (ESubsup (EIdentifier "T") (ENumber "2") (ENumber "1"))
, ESymbol Rel "="
, ESubsup
    (EIdentifier "M")
    (ESubsup
       (EIdentifier "B")
       (EUnder False (ENumber "4") (EPhantom (EText TextNormal "0")))
       (ENumber "3"))
    (ESubsup
       (EIdentifier "T")
       (ENumber "2")
       (EOver False (ENumber "1") (EPhantom (EText TextNormal "0"))))
]
>>> mml
<?xml version='1.0' ?>
<math display="block" xmlns="http://www.w3.org/1998/Math/MathML">
  <mrow>
    <msubsup>
      <mi>M</mi>
      <msubsup>
        <mi>B</mi>
        <mn>4</mn>
        <mn>3</mn>
      </msubsup>
      <msubsup>
        <mi>T</mi>
        <mn>2</mn>
        <mn>1</mn>
      </msubsup>
    </msubsup>
    <mo>=</mo>
    <msubsup>
      <mi>M</mi>
      <msubsup>
        <mi>B</mi>
        <munder>
          <mn>4</mn>
          <mphantom>
            <mtext mathvariant="normal">0</mtext>
          </mphantom>
        </munder>
        <mn>3</mn>
      </msubsup>
      <msubsup>
        <mi>T</mi>
        <mn>2</mn>
        <mover>
          <mn>1</mn>
          <mphantom>
            <mtext mathvariant="normal">0</mtext>
          </mphantom>
        </mover>
      </msubsup>
    </msubsup>
  </mrow>
</math>