code: function showAST(node) {
    if (node === null) {
      return 'null';
    } else if (node instanceof Array) {
      return '[\n' + showASTs(node).join(',\n') + '\n]';
    } else if (node instanceof Token) {
      return node.toString();
    } else {
      let tag = Symbol.keyFor(node.tag).substring(2);
      return tag + '(\n' + showASTs(node.children).join(',\n') + '\n)';
    }
  }
docs: /* Forward declaration (for ESLint)