code: def test_get_data_custom_validation_strategy(
      cfg_mock, read_dataframe_drop_missing_labels_mock
  ):
      cfg_mock.dataset.validation_strategy = "custom"
      train_df, val_df = load_train_valid_data(cfg_mock)
      assert len(train_df), len(val_df) == 100
  
file_path: h2o-llmstudio/tests/src/utils/test_data_utils.py
imports: import os
  import pathlib
  import random
  import unittest
  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
  from llm_studio.src.utils.data_utils import load_train_valid_data
label_desc: Use image node_id 4 for calling a global function with example usage: test_get_data_custom_validation_strategy(cfg_mock, read_dataframe_drop_missing_labels_mock) without return types