<sdf version='1.7'>
  <model name="top">
    <frame name="F"/>
    <model name="nested" canonical_link="link2">
      <link name="link1"/>
      <link name="link2"/>
    </model>
    <model name="shallow">
      <frame name="F"/>
      <model name="deep">
        <model name="deeper">
          <model name="deepest">
            <link name="deepest_link"/>
          </model>
        </model>
      </model>
    </model>
  </model>
</sdf>
