ck is made as to whether <code>i</code> names one of the standard <code>oce</code> slots.
If so, <code>[[</code> returns the slot contents of that slot.  Thus, <code>x[["metadata"]]</code>
will retrieve the <code>metadata</code> slot, while <code>x[["data"]]</code> and
<code>x[["processingLog"]]</code> return those slots.</p></li>
<li><p>If <code>i</code> is a string ending in the <code>"Unit"</code>, then the characters preceding
that string are taken to be the name of an item in the data object, and a
lis