class_docstr: Dataset for Causal Language modeling.
code: def __len__(self) -> int:
      return len(self.conversation_chain_handler)
  
imports: import codecs
  import collections.abc
  import logging
  from typing import Any, Dict, List, Tuple, Union
  import numpy
  import pandas
  import torch
  from torch.utils.data import Dataset
  from llm_studio.src.datasets.conversation_chain_handler import ConversationChainHandler
  from llm_studio.src.datasets.text_utils import get_tokenizer
label_desc: Use image node_id 2 for calling the CustomDataset obj's underlying member method code with example usage: obj.__len__() and returns: len