code: function ttf2woff2Transform() {
    // Return a callback function handling the buffered content
    return function ttf2woff2TransformCb(err, buf, cb) {
  
      // Handle any error
      if(err) {
        return cb(new PluginError(PLUGIN_NAME, err, { showStack: true }));
      }
  
      // Use the buffered content
      try {
        buf = ttf2woff2(buf);
        return cb(null, buf);
      } catch(err2) {
        return cb(new PluginError(PLUGIN_NAME, err2, { showStack: true }));
      }
  
    };
  }
docs: File level transform function