FIX(protocol): make tag optional for getPreviousResponse

     *                               request in a TCP connection

     * @param {Buffer} keyArg - key for the value that is being returned.

     * @param {number} dbVersionArg - the version of the object in the DB

     * @param {Buffer} tagArg - the hash of the value to put.

     * @param {number} code - response code (SUCCESS, FAIL)

     * @param {Buffer} errorMessageArg - Detailed error message.

     * @param {string} algorithm - algorithm used for the tag.

     * @param {Object} optionsArg - optional :

     *                  {string} [options.algorithm] - algorithm used for the

     *                                                 tag

     *                  {Buffer} [options.tag] - the hash of the value to put.

     * @returns {Kinetic} - message structure following the kinetic protocol

     */

    constructor(

        ackSequence, keyArg, dbVersionArg, tagArg, code, errorMessageArg,

        algorithm) {

        ackSequence, keyArg, dbVersionArg, code, errorMessageArg, optionsArg) {

        super();

        const options = optionsArg || {};

        let tag = null;

        if (options.tag)

            tag = validateVersionArgument(options.tag);

        const detailedMessage = validateBufferOrStringArgument(errorMessageArg);

        const key = validateBufferOrStringArgument(keyArg);

        const tag = validateVersionArgument(tagArg);

        const dbVersion = validateVersionArgument(dbVersionArg);

        this.setCommand({

                    key,

                    dbVersion,

                    tag,

                    algorithm: validateAlgo(algorithm) ||

                        algorithms.SHA1,

                    algorithm: tag ? validateAlgo(options.algorithm) ||

                        algorithms.SHA1 : null,

                },

            },

            status: {