code: function Attachment(options) {
      this.fileName = options.fileName;
      this.contents = options.contents;
      this.filePath = options.filePath;
      this.streamSource = options.streamSource;
      this.contentType = options.contentType;
      this.cid = options.cid;
  }
docs: Attachment constructor.
  Options of nodemailer attachment are available
  @constructor