public function predict(Dataset $dataset) : array
    {
        if (!$this->trained) {
            throw new RuntimeException('The learner has not'
                . ' been trained.');
        }
        
        $n = $dataset->numRows();

        $predictions = [];

        for ($i = 0; $i < $n; $i++) {
            $predictions[] = $this->strategy->guess();
        }

        return $predictions;
    }