ut the set of variables or properties that can be resolved for the given <code>base</code>
 object. One use for this method is to assist tools in auto-completion.

 <p>
 If the <code>base</code> parameter is <code>null</code>, the resolver must enumerate the list of top-level variables
 it can resolve.
 </p>

 <p>
 The <code>Iterator</code> returned must contain zero or more instances of <a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.desktop/java/beans/FeatureDescriptor.html?is-external=tr