code: function SymmetricallyEncrypted() {
    /**
     * Packet type
     * @type {module:enums.packet}
     */
    this.tag = enums.packet.symmetricallyEncrypted;
    /**
     * Encrypted secret-key data
     */
    this.encrypted = null;
    /**
     * Decrypted packets contained within.
     * @type {module:packet.List}
     */
    this.packets = null;
    /**
     * When true, decrypt fails if message is not integrity protected
     * @see module:config.ignore_mdc_error
     */
    this.ignore_mdc_error = config.ignore_mdc_error;
  }
docs: Implementation of the Symmetrically Encrypted Data Packet (Tag 9)
  
  {@link https://tools.ietf.org/html/rfc4880#section-5.7|RFC4880 5.7}:
  The Symmetrically Encrypted Data packet contains data encrypted with a
  symmetric-key algorithm. When it has been decrypted, it contains other
  packets (usually a literal data packet or compressed data packet, but in
  theory other Symmetrically Encrypted Data packets or sequences of packets
  that form whole OpenPGP messages).
  @memberof module:packet
  @constructor