i</code> is <code>"?"</code>, then the return value is a list
containing four items, each of which is a character vector
holding the names of things that can be accessed 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 <em>not</em> authoritative, because
information provided by different instruments is so varied.</p></li>
<li><p>I