How to use the @authenio/xml-encryption.decrypt function in @authenio/xml-encryption

return new Promise<[string, any]>((resolve, reject) => {
        // Implement decryption first then check the signature
        if (!entireXML) {
          return reject(new Error('ERR_UNDEFINED_ASSERTION'));
        }
        // Perform encryption depends on the setting of where the message is sent, default is false
        const hereSetting = here.entitySetting;
        const xml = new dom().parseFromString(entireXML);
        const encryptedAssertions = select("/*[contains(local-name(), 'Response')]/*[local-name(.)='EncryptedAssertion']", xml) as Node[];
        if (!Array.isArray(encryptedAssertions)) {
          throw new Error('ERR_UNDEFINED_ENCRYPTED_ASSERTION');
        }
        if (encryptedAssertions.length !== 1) {
          throw new Error('ERR_MULTIPLE_ASSERTION');
        }
        return xmlenc.decrypt(encryptedAssertions[0].toString(), {
          key: utility.readPrivateKey(hereSetting.encPrivateKey, hereSetting.encPrivateKeyPass),
        }, (err, res) => {
          if (err) {
            console.error(err);
            return reject(new Error('ERR_EXCEPTION_OF_ASSERTION_DECRYPTION'));
          }
          if (!res) {
            return reject(new Error('ERR_UNDEFINED_ENCRYPTED_ASSERTION'));
          }
          const assertionNode = new dom().parseFromString(res);
          xml.replaceChild(assertionNode, encryptedAssertions[0]);
          return resolve([xml.toString(), res]);
        });
      });
    },