static filterVariantsByHDRLevel_(variants, hdrLevel) {
    if (hdrLevel == 'AUTO') {
      const someHLG = variants.some((variant) => {
        if (variant.video && variant.video.hdr &&
            variant.video.hdr == 'HLG') {
          return true;
        }
        return false;
      });
      const device = shaka.device.DeviceFactory.getDevice();
      hdrLevel = device.getHdrLevel(someHLG);
    }
    return variants.filter((variant) => {
      if (variant.video && variant.video.hdr && variant.video.hdr != hdrLevel) {
        return false;
      }
      return true;
    });
  }
Filters variants according to the given hdr level config.

@param {!Array<shaka.extern.Variant>} variants
@param {string} hdrLevel
@private