public function setMaxChoices($maxChoices)
    {
        if (is_int($maxChoices) === true && $maxChoices >= 0) {
            $this->maxChoices = $maxChoices;
        } else {
            $msg = "The 'maxChoices' argument must be a positive (>= 0) integer, '" . gettype($maxChoices) . "' given.";
            throw new InvalidArgumentException($msg);
        }
    }