How to use the pkcs11js.CKA_VALUE_LEN function in pkcs11js

prime1: { v: pkcs11.CKA_PRIME_1, t: TYPE_BUFFER },
  prime2: { v: pkcs11.CKA_PRIME_2, t: TYPE_BUFFER },
  exp1: { v: pkcs11.CKA_EXPONENT_1, t: TYPE_BUFFER },
  exp2: { v: pkcs11.CKA_EXPONENT_2, t: TYPE_BUFFER },
  coefficient: { v: pkcs11.CKA_COEFFICIENT, t: TYPE_BUFFER },
  prime: { v: pkcs11.CKA_PRIME, t: TYPE_BUFFER },
  subprime: { v: pkcs11.CKA_SUBPRIME, t: TYPE_BUFFER },
  base: { v: pkcs11.CKA_BASE, t: TYPE_BUFFER },

  /* CKA_PRIME_BITS and CKA_SUB_PRIME_BITS are new for v2.11 */
  primeBits: { v: pkcs11.CKA_PRIME_BITS, t: TYPE_NUMBER },
  subprimeBits: { v: pkcs11.CKA_SUBPRIME_BITS, t: TYPE_NUMBER },
  /* (To retain backwards-compatibility) */

  valueBits: { v: pkcs11.CKA_VALUE_BITS, t: TYPE_NUMBER },
  valueLen: { v: pkcs11.CKA_VALUE_LEN, t: TYPE_NUMBER },

  /* CKA_EXTRACTABLE, CKA_LOCAL, CKA_NEVER_EXTRACTABLE,
 * CKA_ALWAYS_SENSITIVE, CKA_MODIFIABLE, CKA_ECDSA_PARAMS,
 * and CKA_EC_POINT are new for v2.0 */
  extractable: { v: pkcs11.CKA_EXTRACTABLE, t: TYPE_BOOL },
  local: { v: pkcs11.CKA_LOCAL, t: TYPE_BOOL },
  neverExtractable: { v: pkcs11.CKA_NEVER_EXTRACTABLE, t: TYPE_BOOL },
  alwaysSensitive: { v: pkcs11.CKA_ALWAYS_SENSITIVE, t: TYPE_BOOL },

  /* CKA_KEY_GEN_MECHANISM is new for v2.11 */
  keyGenMechanism: { v: pkcs11.CKA_KEY_GEN_MECHANISM, t: TYPE_NUMBER },

  modifiable: { v: pkcs11.CKA_MODIFIABLE, t: TYPE_BOOL },

  /* CKA_ECDSA_PARAMS is deprecated in v2.11,
 * CKA_EC_PARAMS is preferred. */

_pkcs11GenerateKey(pkcs11, pkcs11Session, pkcs11Token) {
		const ski = this._ski();
		const secretKeyTemplate = [
			{type: pkcs11js.CKA_ID, value: ski},
			{type: pkcs11js.CKA_CLASS, value: pkcs11js.CKO_SECRET_KEY},
			{type: pkcs11js.CKA_KEY_TYPE, value: pkcs11js.CKK_AES},
			{type: pkcs11js.CKA_VALUE_LEN, value: this._keySize / 8},
			{type: pkcs11js.CKA_ENCRYPT, value: true},
			{type: pkcs11js.CKA_DECRYPT, value: true},
			/*
			 * If user is logged in:
			 *   - key will be private
			 *   - key will be non-ephemeral by user request
			 * If user is not logged in:
			 *   - key will be public
			 *   - key will be ephermal regardless of user request
			 *
			 * Note that public and private here means publically and privately
			 * accessible, respectively, and has nothing to do with public and
			 * private key pair.
			 */
			{type: pkcs11js.CKA_PRIVATE, value: this._pkcs11Login},
			{type: pkcs11js.CKA_TOKEN, value: this._pkcs11Login && pkcs11Token}

modulus: { v: pkcs11.CKA_MODULUS, t: TYPE_BUFFER },
    modulusBits: { v: pkcs11.CKA_MODULUS_BITS, t: TYPE_NUMBER },
    publicExponent: { v: pkcs11.CKA_PUBLIC_EXPONENT, t: TYPE_BUFFER },
    privateExponent: { v: pkcs11.CKA_PRIVATE_EXPONENT, t: TYPE_BUFFER },
    prime1: { v: pkcs11.CKA_PRIME_1, t: TYPE_BUFFER },
    prime2: { v: pkcs11.CKA_PRIME_2, t: TYPE_BUFFER },
    exp1: { v: pkcs11.CKA_EXPONENT_1, t: TYPE_BUFFER },
    exp2: { v: pkcs11.CKA_EXPONENT_2, t: TYPE_BUFFER },
    coefficient: { v: pkcs11.CKA_COEFFICIENT, t: TYPE_BUFFER },
    prime: { v: pkcs11.CKA_PRIME, t: TYPE_BUFFER },
    subprime: { v: pkcs11.CKA_SUBPRIME, t: TYPE_BUFFER },
    base: { v: pkcs11.CKA_BASE, t: TYPE_BUFFER },
    primeBits: { v: pkcs11.CKA_PRIME_BITS, t: TYPE_NUMBER },
    subprimeBits: { v: pkcs11.CKA_SUBPRIME_BITS, t: TYPE_NUMBER },
    valueBits: { v: pkcs11.CKA_VALUE_BITS, t: TYPE_NUMBER },
    valueLen: { v: pkcs11.CKA_VALUE_LEN, t: TYPE_NUMBER },
    extractable: { v: pkcs11.CKA_EXTRACTABLE, t: TYPE_BOOL },
    local: { v: pkcs11.CKA_LOCAL, t: TYPE_BOOL },
    neverExtractable: { v: pkcs11.CKA_NEVER_EXTRACTABLE, t: TYPE_BOOL },
    alwaysSensitive: { v: pkcs11.CKA_ALWAYS_SENSITIVE, t: TYPE_BOOL },
    keyGenMechanism: { v: pkcs11.CKA_KEY_GEN_MECHANISM, t: TYPE_NUMBER },
    modifiable: { v: pkcs11.CKA_MODIFIABLE, t: TYPE_BOOL },
    paramsECDSA: { v: pkcs11.CKA_ECDSA_PARAMS, t: TYPE_BUFFER },
    paramsEC: { v: pkcs11.CKA_EC_PARAMS, t: TYPE_BUFFER },
    pointEC: { v: pkcs11.CKA_EC_POINT, t: TYPE_BUFFER },
    secondaryAuth: { v: pkcs11.CKA_SECONDARY_AUTH, t: TYPE_BOOL },
    authPinFlags: { v: pkcs11.CKA_AUTH_PIN_FLAGS, t: TYPE_BUFFER },
    alwaysAuth: pkcs11.CKA_ALWAYS_AUTHENTICATE,
    wrapWithTrusted: pkcs11.CKA_WRAP_WITH_TRUSTED,
    wrapTemplate: pkcs11.CKA_WRAP_TEMPLATE,
    unwrapTemplate: pkcs11.CKA_UNWRAP_TEMPLATE,
    otpFormat: pkcs11.CKA_OTP_FORMAT,

];

		/*
			* Call PKCS11 API to generate the key.
			*/
		const handle = pkcs11.C_GenerateKey(
			pkcs11Session, {mechanism: pkcs11js.CKM_AES_KEY_GEN},
			secretKeyTemplate);
		/*
			* Template for querying key attributes (debug only).
			*/
		const objectTemplate = [
			{type: pkcs11js.CKA_ID},
			{type: pkcs11js.CKA_CLASS},
			{type: pkcs11js.CKA_KEY_TYPE},
			{type: pkcs11js.CKA_VALUE_LEN},
			{type: pkcs11js.CKA_ENCRYPT},
			{type: pkcs11js.CKA_DECRYPT},
			{type: pkcs11js.CKA_PRIVATE},
			{type: pkcs11js.CKA_TOKEN}
		];
		logger.debug(__func() + 'secretKey: ' + util.inspect(
			this._pkcs11GetAttributeValue(
				pkcs11, pkcs11Session, handle, objectTemplate),
			{depth: null}));

		return {ski, key: handle};
	}