def _filter(self) -> None:
        """Filter CIFAR10 dataset: select images of 'dog', 'frog',
        'horse', 'ship', 'truck' classes."""
        mask = np.array(self._cifar.targets) >= self._split
        self._cifar.data = self._cifar.data[mask]
        self._cifar.targets = np.array(self._cifar.targets)[mask].tolist()
Filter CIFAR10 dataset: select images of 'dog', 'frog',
        'horse', 'ship', 'truck' classes.
catalyst/contrib/datasets/cifar.py