class_docstr: The dataset class for fine tune RETRO models.
  
  Args:
      data (list[strings], list[dicts]): (1) paths to .jsonl or .json files, (2) dict objects corresponding to each input example
      tokenizer (tokenizer): Tokenizer from frozen language model
      task_templates (dict): Dictionary containing all task template information needed to format prompts. Created in the GPTPromptLearningModel class.
      pad_token_id (int): ID of pad token from tokenizer
      max_seq_length (int): maximum sequence length for each dataset examples. Examples will either be truncated to fit this length or dropped if they cannot be truncated.
      min_seq_length (int): min length of each data example in the dataset. Data examples will be dropped if they do not meet the min length requirements. 
      add_bos (bool): Whether to add a beginning of sentence token to each data example
      add_eos (bool): Whether to add an end of sentence token to each data example
      for_train (bool): Whether you're creating a dataset for training or inference
      tokens_to_generate (int): (inference only) Number of tokens to generate during inference
code: def __getitem__(self, idx):
      if isinstance(idx, np.int64):
          idx = idx.item()
  
      if self.samples_mapping is not None:
          assert idx < len(self.samples_mapping)
          idx, _, _ = self.samples_mapping[idx]
          if isinstance(idx, np.uint32):
              idx = idx.item()
  
      assert idx < len(self.indexed_dataset)
      example = self.indexed_dataset[idx]
      return self._process_example(example)
  
file_path: NeMo/nemo/collections/nlp/data/language_modeling/megatron/retro_fine_tune_dataset.py
imports: from random import sample
  import numpy
  import torch
  from nemo.collections.nlp.data.language_modeling.megatron.dataset_utils import get_samples_mapping
  from nemo.collections.nlp.data.language_modeling.text_memmap_dataset import JSONLMemMapDataset
  from nemo.core import Dataset
  from nemo.utils import logging
label_desc: Use image node_id 4 for calling the RetroQAFineTuneDataset obj's underlying member method code with example usage: obj.__getitem__(idx) and returns: self