example_dataset_dataloader.py

class YourDataset(torch.utils.data.Dataset):
    def __init__(self, ...):
        ...

   def __len__(self):
       ...
       return num_all_examples

   def __getitem__(self, idx):
       ...
       return one_image, one_caption

dataset = YourDataset(...)
loader = torch.utils.data.DataLoader(dataset, ...)

for batch_images, batch_captions in loader:
    # Train your network
    ....