mlNodeGetContent() and hence is recursive.</li>
  <li><code>parent</code> , <code>children</code>, <code>last</code>,
    <code>next</code>, <code>prev</code>, <code>doc</code>,
    <code>properties</code>: pointing to the associated element in the tree,
    those may return None in case no such link exists.</li>
</ul><p>Also note the need to explicitly deallocate documents with freeDoc() .
Reference counting for libxml2 trees would need quite a lot of work to
function properly, and rather than risk memory 