function _getKeys(json, aKeys) {
        var aKey,
            sKey,
            oItem;

        for (sKey in json) {

            if (json.hasOwnProperty(sKey)) {
                oItem = json[sKey];
                if (_isObject(oItem) || _isArray(oItem)) {
                    aKeys = aKeys.concat(unique(_getKeys(oItem, aKeys)));
                }
                if (isNaN(Number(sKey))) {
                    if (!contains(aKeys, sKey)) {
                        _nCode += 1;
                        aKey = [];
                        aKey.push(_getSpecialKey(_numberToKey(_nCode)), sKey);
                        aKeys.push(aKey);
                    }
                }
            }
        }
        return aKeys;
    }
Traverse all the objects looking for keys and set an array with the new keys
@param json
@param aKeys
@returns {*}
@private