def return_all_items(dataset):
  all_items = []
  for i in range(len(dataset)):
    all_items.append(dataset[i])
  return all_items

list1 = return_all_items(original_data)
list2 = return_all_items(transformed_data)
list1.extend(list2)

then converting the list to dataset object
class AugmentedDataset(Dataset):
  
  def __init__(self, combined_list, transform=None):
    self.combined_list = combined_list
    
  def __len__(self):
    return len(self.combined_list)
  
  def __getitem__(self, idx):
    sample = self.combined_list[idx]      
    return sample
  
augmented_dataset = AugmentedDataset(list1)