code: function encodeAttachmentCert(buffer, offset, attachment_data) {
      offset += encodeString(buffer, attachment_data.symbol, offset);
      offset += encodeString(buffer, attachment_data.owner, offset);
      offset += encodeString(buffer, attachment_data.address, offset);
      offset = buffer.writeUInt32LE(attachment_data.cert, offset);
      offset = buffer.writeUInt8(attachment_data.status, offset);
      if (attachment_data.content) {
          offset += encodeString(buffer, attachment_data.content, offset);
      }
      return offset;
  }
docs: Helper function to encode the attachment for a certificate.
  @param {Buffer} buffer
  @param {Number} offset
  @param {Number} attachment_data
  @returns {Number} New offset
  @throws {Error}