docs: private void verifyReservedBit2(WebSocketFrame frame) throws WebSocketException
      {
          if (frame.getRsv2() == false)
          {
              // No problem.
              return;
          }
  
          // The RSV2 bit of a frame is set unexpectedly.
          throw new WebSocketException(
              WebSocketError.UNEXPECTED_RESERVED_BIT, "The RSV2 bit of a frame is set unexpectedly.");
      }