export() {
    $.checkState(this.#round > 0, 'Cannot export a session that has not started');
    $.checkState(!this.isSignatureReady(), 'Cannot export a completed session. The signature is ready with getSignature()');
    
    const sessionBytes = this.#dsg.dsgSessionBytes || this.#dsg.dsgSession?.toBytes();
    const payload = this.#round +
      ':' + this.#partySize +
      ':' + this.#minSigners +
      ':' + this.#partyId +
      ':' + this.#derivationPath +
      ':' + Buffer.from(sessionBytes).toString('base64') +
      ':' + this.#messageHash.toString('base64');
    const buf = encrypt(Buffer.from(payload, 'utf8'), this.#authKey.publicKey, this.#authKey);
    return buf.toString('base64');
  }
Export the signing session to a base64 encoded string
@returns {string} Base64 encoded session string