code: function receiveIframeMessage(event) {
      const data = uiFns.receiveIframeMessageBoilerplate(event);
  
      if (!data) {
        return;
      }
  
      if (data.annotationsOverlay) {
        if (data.annotationsOverlay === 'on') {
          // Can assume we're not viewing the Mustache Browser.
          annotationsViewer.mustacheBrowser = false;
          annotationsViewer.viewall = data.viewall || false;
  
          annotationsViewer.updateAnnotations(data.annotations, data.patternPartial);
        }
        else {
          annotationsViewer.closeAnnotations();
        }
      }
      else if (data.annotationNumber) {
        annotationsViewer.moveTo(data.annotationNumber);
      }
      else if (data.annotationsViewallClick) {
        annotationsViewer.openAnnotations();
      }
      else if (typeof data.annotationsMustacheBrowser === 'boolean') {
        annotationsViewer.mustacheBrowser = data.annotationsMustacheBrowser;
      }
      else if (typeof data.annotationsViewall === 'boolean') {
        annotationsViewer.viewall = data.annotationsViewall;
      }
  
      switch (data.event) {
        case 'patternlab.keyPress':
          switch (data.keyPress) {
            case 'ctrl+shift+a':
              annotationsViewer.toggleAnnotations();
  
              break;
  
            case 'esc':
              if (annotationsViewer.annotationsActive) {
                annotationsViewer.closeAnnotations();
              }
  
              break;
          }
  
          break;
      }
    }
docs: This gets attached as an event listener, so do not use arrow function notation.
  
  @param {object} event - Event info.