code: function Literal(date=new Date()) {
    this.tag = enums.packet.literal;
    this.format = 'utf8'; // default format for literal data packets
    this.date = util.normalizeDate(date);
    this.text = null; // textual data representation
    this.data = null; // literal data representation
    this.filename = 'msg.txt';
  }
docs: Implementation of the Literal Data Packet (Tag 11)
  
  {@link https://tools.ietf.org/html/rfc4880#section-5.9|RFC4880 5.9}:
  A Literal Data packet contains the body of a message; data that is not to be
  further interpreted.
  @param {Date} date the creation date of the literal package
  @memberof module:packet
  @constructor