 with <code>[[</code>.
The <code>data</code> and <code>metadata</code> items hold the names of
entries in the object's data and metadata
slots, respectively. The <code>dataDerived</code>
and <code>metadataDerived</code> items are each NULL, because
no derived values are defined by <a href="bremen-class.html">bremen</a> objects.</p></li>
</ul></div>
    <div class="section level2">
    <h2 id="details-of-the-general-method">Details of the General Method<a class="anchor" aria-label="anchor" href="#details-of-