public function train(Dataset $dataset) : void
    {
        if ($this->type() === self::CLASSIFIER or $this->type() === self::REGRESSOR) {
            if (!$dataset instanceof Labeled) {
                throw new InvalidArgumentException('This estimator requires a'
                    . ' labeled training set.');
            }
        }

        DatasetIsCompatibleWithEstimator::check($dataset, $this);

        $p = (int) round($this->ratio * $dataset->numRows());

        $this->ensemble = [];

        Loop::run(function () use ($dataset, $p) {
            $pool = new DefaultPool($this->workers);

            $coroutines = [];

            for ($i = 0; $i < $this->estimators; $i++) {
                $estimator = clone $this->base;

                $subset = $dataset->randomSubsetWithReplacement($p);

                $task = new CallableTask(
                    [$this, '_train'],
                    [$estimator, $subset]
                );

                $coroutines[] = call(function () use ($pool, $task) {
                    return yield $pool->enqueue($task);
                });
            }

            $this->ensemble = yield all($coroutines);
            
            return yield $pool->shutdown();
        });
    }