docs: public static synchronized PrivacyListManager getInstanceFor(XMPPConnection connection) {
          PrivacyListManager plm = INSTANCES.get(connection);
          if (plm == null) {
              plm = new PrivacyListManager(connection);
              // Register the new instance and associate it with the connection
              INSTANCES.put(connection, plm);
          }
          return plm;
      }