docs: private String pipelineToString() {
          StringBuilder sb = new StringBuilder("in-pipeline[");
          InboundHandler[] handlers = this.handlers;
          for (int k = 0; k < handlers.length; k++) {
              if (k > 0) {
                  sb.append("->-");
              }
              sb.append(handlers[k].getClass().getSimpleName());
          }
          sb.append(']');
          return sb.toString();
      }