code: def test_conversation_chain_handler(cfg, df):
      handler = ConversationChainHandler(df, cfg)
  
      assert len(handler) == 2, len(handler)
  
      data = handler[0]
      assert data == {
          "prompts": ["prompt1", "prompt2", "prompt3", "prompt4"],
          "answers": ["answer1", "answer2", "answer3", "answer4"],
          "systems": ["system1", "system2", "system3", "system4"],
      }
  
      data = handler[1]
      assert data == {
          "prompts": ["p1", "p2", "p3", "p4"],
          "answers": ["a1", "a2", "a3", "a4"],
          "systems": ["s1", "s2", "s3", "s4"],
      }
  
file_path: h2o-llmstudio/tests/src/datasets/test_conversation_chain_handler.py
imports: import time
  from unittest import mock
  from unittest.mock import MagicMock
  import pandas
  import pytest
  from llm_studio.app_utils.default_datasets import prepare_default_dataset_causal_language_modeling
  from llm_studio.src.datasets.conversation_chain_handler import ConversationChainHandler
label_desc: Use image node_id 4 for calling a global function with example usage: test_conversation_chain_handler(cfg, df) without return types