code: public WriteFuture stopSsl(IoSession session) throws SSLException {
          SslHandler handler = getSslSessionHandler(session);
          NextFilter nextFilter = (NextFilter) session.getAttribute(NEXT_FILTER);
          WriteFuture future;
          synchronized (handler) {
              future = initiateClosure(nextFilter, session);
          }
  
          handler.flushScheduledEvents();
  
          return future;
      }
docs: Stops the SSL session by sending TLS <tt>close_notify</tt> message to
  initiate TLS closure.
  
  @param session the {@link IoSession} to initiate TLS closure
  @throws SSLException if failed to initiate TLS closure
  @throws IllegalArgumentException if this filter is not managing the specified session