public function getPermutations(array $sourceDataSet, $subsetSize = null)
    {
        $combinationMap = $this->_combination->getCombinations($sourceDataSet, $subsetSize);
        
        $permutationsMap = [];
        foreach ($combinationMap as $combination) {
            $permutationsMap = array_merge(
                $permutationsMap,
                $this->_findPermutations($combination)
            );
        }
        
        return $permutationsMap;
    }