code: def __getitem__(self, idx):
      return self.samples[idx]
  
file_path: llama-recipes/src/llama_recipes/data/concatenator.py
imports: from tqdm import tqdm
  from itertools import chain
  from torch.utils.data import Dataset
label_desc: Use image node_id 2 for calling the ConcatDataset obj's underlying member method code with example usage: obj.__getitem__(idx) and returns: self