code: function(content) {
        this.waiting = false;
        if (typeof content !== 'undefined') {
          this.previous_content = this.content;
          this.content = content;
        }
        if (this.callbacks.length > 0) {
          this.then(this.callbacks.shift());
        }
      }
docs: Resume the queue, setting `content` to be used in the next operation. See `wait()` for an example.