code: function defaultOptions() {
      return {
          optimistic: false,
          directive: false,
          nodejsScope: false,
          impliedStrict: false,
          sourceType: "script",  // one of ['script', 'module']
          ecmaVersion: 5,
          childVisitorKeys: null,
          fallback: "iteration"
      };
  }
docs: Set the default options
  @returns {Object} options