docs: protected static FORK getFORK(JChannel ch, ProtocolStack.Position position, Class<? extends Protocol> neighbor,
                                    boolean create_fork_if_absent) throws Exception {
          ProtocolStack stack=ch.getProtocolStack();
          FORK fork=stack.findProtocol(FORK.class);
          if(fork == null) {
              if(!create_fork_if_absent)
                  throw new IllegalArgumentException("FORK not found in main stack");
              fork = new FORK();
              fork.setProtocolStack(stack);
              stack.insertProtocol(fork, position, neighbor);
          }
          return fork;
      }