ref="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/util/Set.html?is-external=true" title="class or interface in java.util" class="externalLink"><code>Set</code></a>. Callers of the API should be aware that
 the returned <a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/util/Set.html?is-external=true" title="class or interface in java.util" class="externalLink"><code>Set</code></a> may be immutable, or a copy, and that, in any case,
 it should not be modified by t