code: function svg2ttfTransform(options) {
    // Return a callback function handling the buffered content
    return function svg2ttfTransformCb(err, buf, cb) {
  
      // Handle any error
      if(err) {
        cb(new gutil.PluginError(PLUGIN_NAME, err, { showStack: true }));
        return;
      }
  
      // Use the buffered content
      try {
        buf = Buffer.from(svg2ttf(String(buf), {
          ts: options.timestamp,
          copyright: options.copyright,
          version: options.version,
        }).buffer);
      } catch (err2) {
        cb(new gutil.PluginError(PLUGIN_NAME, err2, { showStack: true }));
        return;
      }
      cb(null, buf);
    };
  }
docs: File level transform function