public function setGapChoices(GapChoiceCollection $gapChoices)
    {
        if (count($gapChoices) > 0) {
            $this->gapChoices = $gapChoices;
        } else {
            $msg = "A GapMatchInteraction object must be composed of at least one GapChoice object, none given.";
            throw new InvalidArgumentException($msg);
        }
    }