toggleHighlightLayer (layerNameToHighlight) {
    let i
    const curNames = []
    const numLayers = this.editor.svgCanvas.getCurrentDrawing().getNumLayers()
    for (i = 0; i < numLayers; i++) {
      curNames[i] = this.editor.svgCanvas.getCurrentDrawing().getLayerName(i)
    }

    if (layerNameToHighlight) {
      curNames.forEach((curName) => {
        if (curName !== layerNameToHighlight) {
          this.editor.svgCanvas
            .getCurrentDrawing()
            .setLayerOpacity(curName, 0.5)
        }
      })
    } else {
      curNames.forEach((curName) => {
        this.editor.svgCanvas.getCurrentDrawing().setLayerOpacity(curName, 1.0)
      })
    }
  }
This function highlights the layer passed in (by fading out the other layers).
If no layer is passed in, this function restores the other layers.
@param {string} [layerNameToHighlight]
@returns {void}