code: def test_csv_mem_map_dataset(csv_file):
      """Test for CSV memory-mapped datasets."""
  
      indexed_dataset = text_memmap_dataset.CSVMemMapDataset(
          dataset_paths=[csv_file], data_col=1, header_lines=1
      )
      assert indexed_dataset[0].strip() == "John"
      assert indexed_dataset[1].strip() == "Jane"
      assert indexed_dataset[2].strip() == "Bob"
  
file_path: NeMo/tests/collections/nlp/test_mem_map_dataset.py
imports: import csv
  import json
  import os
  import pytest
  from nemo.collections.nlp.data.language_modeling import text_memmap_dataset
label_desc: Use image node_id 4 for calling a global function with example usage: test_csv_mem_map_dataset(csv_file) without return types