How to use the snapdragon-util.isType function in snapdragon-util

.set('code.open', function(node) {
        adjustTrailingSpace(this);

        var parent = node.parent;
        if (!this.options.literalPre && util.isType(parent.parent, 'pre')) {
          this.emit('\n\n', node);
          this.emit('```');
          this.emit(langMap(node.parent.lang, this.options));
          this.emit('\n');
        } else {
          this.emit(node.parent.delim);
        }
      })
      .set('code.close', function(node) {

Node.prototype.isType = function(type) {
  return utils.isType(this, type);
};