How to use the fabric-common.SigningIdentity function in fabric-common

.then((dsID) => {
			t.equal(dsID._certificate, TEST_CERT_PEM, 'Identity class function tests: deserialized certificate');
			t.equal(dsID._publicKey.isPrivate(), false, 'Identity class function tests: deserialized public key');
			t.equal(dsID._publicKey._key.pubKeyHex, '0452a75e1ee105da7ab3d389fda69d8a04f5cf65b305b49cec7cdbdeb91a585cf87bef5a96aa9683d96bbabfe60d8cc6f5db9d0bc8c58d56bb28887ed81c6005ac', 'Identity class function tests: deserialized public key ecparam check');

			// manually construct a key based on the saved privKeyHex and pubKeyHex
			const f = KEYUTIL.getKey(TEST_KEY_PRIVATE_PEM);
			const testKey = new ecdsaKey(f);
			pubKey = testKey.getPublicKey();

			const signer = new Signer(cryptoUtils, testKey);
			t.equal(signer.getPublicKey().isPrivate(), false, 'Test Signer class getPublicKey() method');

			const signingID = new SigningIdentity(TEST_KEY_PRIVATE_CERT_PEM, pubKey, mspImpl.getId(), cryptoUtils, signer);

			t.throws(
				() => {
					signingID.sign(TEST_MSG, {hashFunction: 'not_a_function'});
				},
				/The "hashFunction" field must be a function/,
				'Test invalid hashFunction parameter for the sign() method'
			);

			const sig = signingID.sign(TEST_MSG);
			t.equal(cryptoUtils.verify(pubKey, sig, TEST_MSG), true, 'Test SigningIdentity sign() method');
			t.equal(signingID.verify(TEST_MSG, sig), true, 'Test Identity verify() method');
			t.end();
		}).catch((err) => {
			t.fail(err.stack ? err.stack : err);

() => {
			new SigningIdentity('cert');
		},
		/Missing required parameter "publicKey"/,

() => {
			new SigningIdentity('cert', 'pubKey', 'mspId', 'cryptoSuite');
		},
		/Missing required parameter "signer"/,

() => {
			new SigningIdentity('cert', 'pubKey');
		},
		/Missing required parameter "mspId"/,