system: You are an expert security code reviewer. You will be shown a source code file. Your task is to name the single function or class that contains the specified CWE vulnerability.

OUTPUT FORMAT: Respond with the exact function or class name (no parentheses, no qualifiers, no module prefixes), wrapped in \boxed{...}. Example: `\boxed{salted_hmac}`. Output the boxed name ONLY -- no explanation, no other text.

user: ```python
import os
import tarfile
import torch
import torch.utils.data as data
import numpy as np
import h5py

from PIL import Image
from scipy import io
from torchvision.datasets.utils import download_url

DATASET_YEAR_DICT = {
    '2012': {
        'url': 'http://host.robots.ox.ac.uk/pascal/VOC/voc2012/VOCtrainval_11-May-2012.tar',
        'filename': 'VOCtrainval_11-May-2012.tar',
        'md5': '6cd6e144f989b92b3379bac3b3de84fd',
        'base_dir': 'VOCdevkit/VOC2012'
    },
    '2011': {
        'url': 'http://host.robots.ox.ac.uk/pascal/VOC/voc2011/VOCtrainval_25-May-2011.tar',
        'filename': 'VOCtrainval_25-May-2011.tar',
        'md5': '6c3384ef61512963050cb5d687e5bf1e',
        'base_dir': 'TrainVal/VOCdevkit/VOC2011'
    },
    '2010': {
        'url': 'http://host.robots.ox.ac.uk/pascal/VOC/voc2010/VOCtrainval_03-May-2010.tar',
        'filename': 'VOCtrainval_03-May-2010.tar',
        'md5': 'da459979d0c395079b5c75ee67908abb',
        'base_dir': 'VOCdevkit/VOC2010'
    },
    '2009': {
        'url': 'http://host.robots.ox.ac.uk/pascal/VOC/voc2009/VOCtrainval_11-May-2009.tar',
        'filename': 'VOCtrainval_11-May-2009.tar',
        'md5': '59065e4b188729180974ef6572f6a212',
        'base_dir': 'VOCdevkit/VOC2009'
    },
    '2008': {
        'url': 'http://host.robots.ox.ac.uk/pascal/VOC/voc2008/VOCtrainval_14-Jul-2008.tar',
        'filename': 'VOCtrainval_11-May-2012.tar',
        'md5': '2629fa636546599198acfcfbfcf1904a',
        'base_dir': 'VOCdevkit/VOC2008'
    },
    '2007': {
        'url': 'http://host.robots.ox.ac.uk/pascal/VOC/voc2007/VOCtrainval_06-Nov-2007.tar',
        'filename': 'VOCtrainval_06-Nov-2007.tar',
        'md5': 'c52e279531787c972589f7e41ab4ae64',
        'base_dir': 'VOCdevkit/VOC2007'
    }
}


class VOCSegmentation(data.Dataset):
    """`Pascal VOC <http://host.robots.ox.ac.uk/pascal/VOC/>`_ Segmentation Dataset.

    Args:
        root (string): Root directory of the VOC Dataset.
        year (string, optional): The dataset year, supports years 2007 to 2012.
        image_set (string, optional): Select the image_set to use, ``train``, ``trainval`` or ``val``
        download (bool, optional): If true, downloads the dataset from the internet and
            puts it in root directory. If dataset is already downloaded, it is not
            downloaded again.
        transform (callable, optional): A function/transform that  takes in an PIL image
            and returns a transformed version. E.g, ``transforms.RandomCrop``
        target_transform (callable, optional): A function/transform that takes in the
            target and transforms it.
    """

    CLASSES = 20
    CLASSES_NAMES = [
        'aeroplane', 'bicycle', 'bird', 'boat', 'bottle',
        'bus', 'car', 'cat', 'chair', 'cow', 'diningtable', 'dog', 'horse',
        'motorbike', 'person', 'potted-plant', 'sheep', 'sofa', 'train',
        'tvmonitor', 'ambigious'
    ]

    def __init__(self,
                 root,
                 year='2012',
                 image_set='train',
                 download=False,
                 transform=None,
                 target_transform=None):
        self.root = os.path.expanduser(root)
        self.year = year
        self.url = DATASET_YEAR_DICT[year]['url']
        self.filename = DATASET_YEAR_DICT[year]['filename']
        self.md5 = DATASET_YEAR_DICT[year]['md5']
        self.transform = transform
        self.target_transform = target_transform
        self.image_set = image_set
        base_dir = DATASET_YEAR_DICT[year]['base_dir']
        voc_root = os.path.join(self.root, base_dir)
        image_dir = os.path.join(voc_root, 'JPEGImages')
        mask_dir = os.path.join(voc_root, 'SegmentationClass')

        if download:
            download_extract(self.url, self.root, self.filename, self.md5)

        if not os.path.isdir(voc_root):
            raise RuntimeError('Dataset not found or corrupted.' +
                               ' You can use download=True to download it')

        splits_dir = os.path.join(voc_root, 'ImageSets/Segmentation')

        split_f = os.path.join(splits_dir, image_set.rstrip('\n') + '.txt')

        if not os.path.exists(split_f):
            raise ValueError(
                'Wrong image_set entered! Please use image_set="train" '
                'or image_set="trainval" or image_set="val"')

        with open(os.path.join(split_f), "r") as f:
            file_names = [x.strip() for x in f.readlines()]

        self.images = [os.path.join(image_dir, x + ".jpg") for x in file_names]
        self.masks = [os.path.join(mask_dir, x + ".png") for x in file_names]
        assert (len(self.images) == len(self.masks))

    def __getitem__(self, index):
        """
        Args:
            index (int): Index

        Returns:
            tuple: (image, target) where target is the image segmentation.
        """
        img = Image.open(self.images[index]).convert('RGB')
        target = Image.open(self.masks[index])

        if self.transform is not None:
            img = self.transform(img)

        if self.target_transform is not None:
            target = np.array(self.target_transform(target)).astype('int32')
            target[target == 255] = -1
            target = torch.from_numpy(target).long()

        return img, target

    @staticmethod
    def _mask_transform(mask):
        target = np.array(mask).astype('int32')
        target[target == 255] = -1
        return torch.from_numpy(target).long()

    def __len__(self):
        return len(self.images)

    @property
    def pred_offset(self):
        return 0


class VOCClassification(data.Dataset):
    """`Pascal VOC <http://host.robots.ox.ac.uk/pascal/VOC/>`_ Segmentation Dataset.

    Args:
        root (string): Root directory of the VOC Dataset.
        year (string, optional): The dataset year, supports years 2007 to 2012.
        image_set (string, optional): Select the image_set to use, ``train``, ``trainval`` or ``val``
        download (bool, optional): If true, downloads the dataset from the internet and
            puts it in root directory. If dataset is already downloaded, it is not
            downloaded again.
        transform (callable, optional): A function/transform that  takes in an PIL image
            and returns a transformed version. E.g, ``transforms.RandomCrop``
    """
    CLASSES = 20

    def __init__(self,
                 root,
                 year='2012',
                 image_set='train',
                 download=False,
                 transform=None):
        self.root = os.path.expanduser(root)
        self.year = year
        self.url = DATASET_YEAR_DICT[year]['url']
        self.filename = DATASET_YEAR_DICT[year]['filename']
        self.md5 = DATASET_YEAR_DICT[year]['md5']
        self.transform = transform
        self.image_set = image_set
        base_dir = DATASET_YEAR_DICT[year]['base_dir']
        voc_root = os.path.join(self.root, base_dir)
        image_dir = os.path.join(voc_root, 'JPEGImages')
        mask_dir = os.path.join(voc_root, 'SegmentationClass')

        if download:
            download_extract(self.url, self.root, self.filename, self.md5)

        if not os.path.isdir(voc_root):
            raise RuntimeError('Dataset not found or corrupted.' +
                               ' You can use download=True to download it')

        splits_dir = os.path.join(voc_root, 'ImageSets/Segmentation')

        split_f = os.path.join(splits_dir, image_set.rstrip('\n') + '.txt')

        if not os.path.exists(split_f):
            raise ValueError(
                'Wrong image_set entered! Please use image_set="train" '
                'or image_set="trainval" or image_set="val"')

        with open(os.path.join(split_f), "r") as f:
            file_names = [x.strip() for x in f.readlines()]

        self.images = [os.path.join(image_dir, x + ".jpg") for x in file_names]
        self.masks = [os.path.join(mask_dir, x + ".png") for x in file_names]
        assert (len(self.images) == len(self.masks))

    def __getitem__(self, index):
        """
        Args:
            index (int): Index

        Returns:
            tuple: (image, target) where target is the image segmentation.
        """
        img = Image.open(self.images[index]).convert('RGB')
        target = Image.open(self.masks[index])

        # if self.transform is not None:
        #     img = self.transform(img)
        if self.transform is not None:
            img, target = self.transform(img, target)

        visible_classes = np.unique(target)
        labels = torch.zeros(self.CLASSES)
        for id in visible_classes:
            if id not in (0, 255):
                labels[id - 1].fill_(1)

        return img, labels

    def __len__(self):
        return len(self.images)


class VOCSBDClassification(data.Dataset):
    """`Pascal VOC <http://host.robots.ox.ac.uk/pascal/VOC/>`_ Segmentation Dataset.

    Args:
        root (string): Root directory of the VOC Dataset.
        year (string, optional): The dataset year, supports years 2007 to 2012.
        image_set (string, optional): Select the image_set to use, ``train``, ``trainval`` or ``val``
        download (bool, optional): If true, downloads the dataset from the internet and
            puts it in root directory. If dataset is already downloaded, it is not
            downloaded again.
        transform (callable, optional): A function/transform that  takes in an PIL image
            and returns a transformed version. E.g, ``transforms.RandomCrop``
    """
    CLASSES = 20

    def __init__(self,
                 root,
                 sbd_root,
                 year='2012',
                 image_set='train',
                 download=False,
                 transform=None):
        self.root = os.path.expanduser(root)
        self.sbd_root = os.path.expanduser(sbd_root)
        self.year = year
        self.url = DATASET_YEAR_DICT[year]['url']
        self.filename = DATASET_YEAR_DICT[year]['filename']
        self.md5 = DATASET_YEAR_DICT[year]['md5']
        self.transform = transform
        self.image_set = image_set
        base_dir = DATASET_YEAR_DICT[year]['base_dir']
        voc_root = os.path.join(self.root, base_dir)
        image_dir = os.path.join(voc_root, 'JPEGImages')
        mask_dir = os.path.join(voc_root, 'SegmentationClass')
        sbd_image_dir = os.path.join(sbd_root, 'img')
        sbd_mask_dir = os.path.join(sbd_root, 'cls')

        if download:
            download_extract(self.url, self.root, self.filename, self.md5)

        if not os.path.isdir(voc_root):
            raise RuntimeError('Dataset not found or corrupted.' +
                               ' You can use download=True to download it')

        splits_dir = os.path.join(voc_root, 'ImageSets/Segmentation')

        split_f = os.path.join(splits_dir, image_set.rstrip('\n') + '.txt')
        sbd_split = os.path.join(sbd_root, 'train.txt')

        if not os.path.exists(split_f):
            raise ValueError(
                'Wrong image_set entered! Please use image_set="train" '
                'or image_set="trainval" or image_set="val"')

        with open(os.path.join(split_f), "r") as f:
            voc_file_names = [x.strip() for x in f.readlines()]

        with open(os.path.join(sbd_split), "r") as f:
            sbd_file_names = [x.strip() for x in f.readlines()]

        self.images = [os.path.join(image_dir, x + ".jpg") for x in voc_file_names]
        self.images += [os.path.join(sbd_image_dir, x + ".jpg") for x in sbd_file_names]
        self.masks = [os.path.join(mask_dir, x + ".png") for x in voc_file_names]
        self.masks += [os.path.join(sbd_mask_dir, x + ".mat") for x in sbd_file_names]
        assert (len(self.images) == len(self.masks))

    def __getitem__(self, index):
        """
        Args:
            index (int): Index

        Returns:
            tuple: (image, target) where target is the image segmentation.
        """
        img = Image.open(self.images[index]).convert('RGB')
        mask_path = self.masks[index]
        if mask_path[-3:] == 'mat':
            target = io.loadmat(mask_path, struct_as_record=False, squeeze_me=True)['GTcls'].Segmentation
            target = Image.fromarray(target, mode='P')
        else:
            target = Image.open(self.masks[index])

        if self.transform is not None:
            img, target = self.transform(img, target)

        visible_classes = np.unique(target)
        labels = torch.zeros(self.CLASSES)
        for id in visible_classes:
            if id not in (0, 255):
                labels[id - 1].fill_(1)

        return img, labels

    def __len__(self):
        return len(self.images)


def download_extract(url, root, filename, md5):
    download_url(url, root, filename, md5)
    with tarfile.open(os.path.join(root, filename), "r") as tar:
        tar.extractall(path=root)


class VOCResults(data.Dataset):
    CLASSES = 20
    CLASSES_NAMES = [
        'aeroplane', 'bicycle', 'bird', 'boat', 'bottle',
        'bus', 'car', 'cat', 'chair', 'cow', 'diningtable', 'dog', 'horse',
        'motorbike', 'person', 'potted-plant', 'sheep', 'sofa', 'train',
        'tvmonitor', 'ambigious'
    ]

    def __init__(self, path):
        super(VOCResults, self).__init__()

        self.path = os.path.join(path, 'results.hdf5')
        self.data = None

        print('Reading dataset length...')
        with h5py.File(self.path , 'r') as f:
            self.data_length = len(f['/image'])

    def __len__(self):
        return self.data_length

    def __getitem__(self, item):
        if self.data is None:
            self.data = h5py.File(self.path, 'r')

        image = torch.tensor(self.data['image'][item])
        vis = torch.tensor(self.data['vis'][item])
        target = torch.tensor(self.data['target'][item])
        class_pred = torch.tensor(self.data['class_pred'][item])

        return image, vis, target, class_pred

```

Name the function or class in this code that contains a `CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')` vulnerability.
Answer: download_extract