I’m trying to solve Cat VS Dog classification problem using pytorch.  So I started by creating  a DataSet class using the following code:
import torchvision.transforms as transforms
import torch

from torch.utils.data import Dataset, DataLoader
import cv2, os

torch.manual_seed(0)
class dogVScat(Dataset):
    def __init__(self, data_dir, transform):
        file_names = os.listdir('train')
        self.full_file_names = [os.path.join('train', file_name) for file_name in file_names]
        self.labels = []
        for file in os.listdir('train'):
            if file.split('.')[0] == 'cat':
                self.labels.append([1, 0])
            else:
                self.labels.append([0, 1])
        self.labels = torch.tensor(self.labels)
        self.transform = transform

        def __len__(self):
            return len(os.listdir('train'))

        def __getitem__(self, idx):
            image = cv2.imread(self.full_file_names[idx])
            image = self.transform(image)
            return image, self.labels[idx]

transformer = transforms.Compose(transforms.ToTensor())

dataset = dogVScat('train', transformer)
image, label = dataset[2]

But when I run the code I face this problem:
Traceback (most recent call last):
  File "C:/Users/BHAAK/Desktop/ML_PATH/dirty-hands/dirty-hands file 3/Project.py", line 30, in <module>
    image, label = dataset[2]
  File "C:\Users\BHAAK\AppData\Local\Programs\Python\Python36\lib\site-packages\torch\utils\data\dataset.py", line 25, in __getitem__
    raise NotImplementedError
NotImplementedError 

Please if any one can help me fix this problem  I will appreciate it…