code: def __len__(self):
      return len(self.query_data)
  
file_path: trl/tests/test_no_peft.py
imports: import sys
  import unittest
  from unittest.mock import patch
  import torch
  from transformers import AutoModelForCausalLM, AutoTokenizer
  from .testing_utils import is_peft_available, require_peft
label_desc: Use image node_id 2 for calling the DummyDataset obj's underlying member method code with example usage: obj.__len__() and returns: len