public function getFeatureImportances(): array
    {
        // Traverse each tree and sum importance of the columns
        $sum = [];
        foreach ($this->classifiers as $tree) {
            /** @var DecisionTree $tree */
            $importances = $tree->getFeatureImportances();

            foreach ($importances as $column => $importance) {
                if (array_key_exists($column, $sum)) {
                    $sum[$column] += $importance;
                } else {
                    $sum[$column] = $importance;
                }
            }
        }

        // Normalize & sort the importance values
        $total = array_sum($sum);
        array_walk($sum, function (&$importance) use ($total): void {
            $importance /= $total;
        });
        arsort($sum);

        return $sum;
    }