code: function _setBooleanOption (key, val) {
    if (is.bool(val)) {
      this.options[key] = val;
    } else {
      throw new Error('Invalid ' + key + ' (boolean) ' + val);
    }
  }
docs: Update a Boolean attribute of the this.options Object.
  @private
  @param {String} key
  @param {Boolean} val
  @throws {Error} Invalid key