merate the
 set of top-level variables that this resolver can evaluate.</dd>
<dt><span class="returnLabel">Returns:</span></dt>
<dd>An <code>Iterator</code> containing zero or more (possibly infinitely more) <code>FeatureDescriptor</code>
 objects, or <code>null</code> if this resolver does not handle the given <code>base</code> object or that the results
 are too complex to represent with this method</dd>
<dt><span class="seeLabel">See Also:</span></dt>
<dd><a href="https://docs.oracle.com/javase/8/docs/ap