code: function (callback) {
              callback = backpack.ensure(callback, this);
  
              if (this.paused) { return callback && callback(new Error('run: already paused')); }
  
              // schedule the pause command as an interrupt and flag that the run is pausing
              this.paused = true;
              this.interrupt('pause', null, callback);
          }
docs: Pause a run
  
  @param {Function} callback