public function offsetSet($offset, $value)
    {
        if (is_null($offset)) {
            $this->_args[count($this->_args)] = $value;
        } else {
            if (is_int($offset)) {
                $this->_args[$offset] = $value;
            } else {
                throw new \Exception('Cannot set offset \''.$offset.'\' of IndexedArray.');
            }
        }
    }