s not provided, the
<code>metadata</code> slot takes preference over the <code>data</code> slot. However, if <code>j</code> is
provided, then it must be either the string <code>"metadata"</code> or <code>"data"</code>, and it
directs where to look.</p></li>
<li><p>If none of the above-listed conditions holds, then <code>NULL</code> is returned.</p></li>
</ol></div>
    <div class="section level2">
    <h2 id="see-also">See also<a class="anchor" aria-label="anchor" href="#see-also"></a></h2>
    <div class="