How to use the webfont function in webfont

function buildFont(config) {
  return webfont({
    files: config.inputFiles,
    fontName: config.fontName,
    startunicode: 0x3400
  })
    .then(content => content)
    .catch(err => console.log(err))
}

generate(callback) {
    const { options } = this;

    nodify(
      webfont(options).then(result => {
        const { fontName, template } = result.config;
        const dest = path.resolve(this.options.dest);

        let destTemplate = dest;

        if (result.template) {
          if (this.options.destTemplate) {
            destTemplate = path.resolve(this.options.destTemplate);
          }

          if (result.usedBuildInTemplate) {
            destTemplate = path.join(destTemplate, `${fontName}.${template}`);
          } else {
            destTemplate = path.join(
              destTemplate,
              path.basename(template).replace(".njk", "")