code: function() {
          this.showReferenceStrip = true;
  
          if (this.sequenceMode) {
              if (this.referenceStrip) {
                  return;
              }
  
              if (this.tileSources.length && this.tileSources.length > 1) {
                  this.referenceStrip = new $.ReferenceStrip({
                      id:          this.referenceStripElement,
                      position:    this.referenceStripPosition,
                      sizeRatio:   this.referenceStripSizeRatio,
                      scroll:      this.referenceStripScroll,
                      height:      this.referenceStripHeight,
                      width:       this.referenceStripWidth,
                      tileSources: this.tileSources,
                      prefixUrl:   this.prefixUrl,
                      viewer:      this
                  });
  
                  this.referenceStrip.setFocus( this._sequenceIndex );
              }
          } else {
              $.console.warn('Attempting to display a reference strip while "sequenceMode" is off.');
          }
      }
docs: Enables and displays the reference strip based on the currently set tileSources.
  Works only when the Viewer has sequenceMode set to true.
  @function