code: function (node, result, cache) {
      result = ''
      // node.body []
      for (var i = 0; i < node.body.length; i++) {
        result += this.gen(node.body[i], result, cache)
      }
      return result
    }
docs: /*
  {
  type: 'match',
  offset: 0,
  text: '',
  body: []
  }