How to use the @zilliqa-js/util.validation.isBech32TestNet function in @zilliqa-js/util

private getAddressType() {
    const addrBool = validation.isAddress(this.raw);
    const base58Bool = validation.isBase58(this.raw);
    const bech32Bool = validation.isBech32(this.raw);
    const bech32TestNetBool = validation.isBech32TestNet(this.raw);
    const checksumBool = isValidChecksumAddress(this.raw);

    if (addrBool === true && checksumBool === false) {
      this.addressType = AddressType.bytes20;
      this.bytes20 = this.raw.startsWith('0x')
        ? this.raw.substring(2)
        : this.raw;
      return;
    }

    if (addrBool === true && checksumBool === true) {
      this.addressType = AddressType.checkSum;
      this.bytes20 = this.raw.toLowerCase().substring(2);
      return;
    }