class_docstr: Dataset for reward model
  
  Args:
      dataset: dataset for reward model
      tokenizer: tokenizer for reward model
      max_length: max length of input
      special_token: special token at the end of sentence
code: def __getitem__(self, idx):
      return (
          self.chosen["input_ids"][idx],
          self.chosen["attention_mask"][idx],
          self.reject["input_ids"][idx],
          self.reject["attention_mask"][idx],
      )
  
file_path: colossalai/applications/Chat/coati/dataset/reward_dataset.py
imports: from typing import Callable
  from torch.utils.data import Dataset
  from tqdm import tqdm
  from .utils import is_rank_0
label_desc: Use image node_id 3 for calling the HhRlhfDataset obj's underlying member method code with example usage: obj.__getitem__(idx) and returns: self,  self,  self,  self