How to use the @mapbox/mapbox-gl-style-spec/deref function in @mapbox/mapbox-gl-style-spec

function ensureHasNoRefs(style) {
  const derefedStyle = {
    ...style,
    layers: deref(style.layers)
  }
  return derefedStyle
}

let spriteImage, spriteImgSize;
  if (spriteImageUrl) {
    const img = new Image();
    img.crossOrigin = 'anonymous';
    img.onload = function() {
      spriteImage = img;
      spriteImgSize = [img.width, img.height];
      olLayer.changed();
      img.onload = null;
    };
    img.src = spriteImageUrl;
  }


  const allLayers = derefLayers(glStyle.layers);

  const layersBySourceLayer = {};
  const mapboxLayers = [];
  let mapboxSource;
  for (let i = 0, ii = allLayers.length; i < ii; ++i) {
    const layer = allLayers[i];
    const layerId = layer.id;
    if (typeof source == 'string' && layer.source == source ||
        source.indexOf(layerId) !== -1) {
      const sourceLayer = layer['source-layer'];
      if (!mapboxSource) {
        mapboxSource = layer.source;
        const source = glStyle.sources[mapboxSource];
        if (!source) {
          throw new Error(`Source "${mapboxSource}" is not defined`);
        }