code: def test_get_prepared_filename():
      filename = "tmp/sample.jsonl"
      prepared_filename = "tmp/sample_prepared.jsonl"
      prepared_train_filename = "tmp/sample_prepared_train.jsonl"
      prepared_val_filename = "tmp/sample_prepared_val.jsonl"
      assert get_prepared_filename(filename) == (
          prepared_filename,
          None,
      )
      assert get_prepared_filename(
          filename, split_train_validation=True
      ) == (
          [
              prepared_train_filename,
              prepared_val_filename,
          ],
          None,
      )
      csv_filename = "tmp/sample.csv"
      prepared_filename = "tmp/sample_prepared.jsonl"
      assert get_prepared_filename(csv_filename) == (
          prepared_filename,
          None,
      )
  
imports: import pandas
  import pytest
  from ..customization_dataset_preparation import convert_into_prompt_completion_only, convert_into_template, drop_duplicated_rows, drop_unrequired_fields, get_common_suffix, get_prepared_filename, parse_template, recommend_hyperparameters, show_first_example_in_df, split_into_train_validation, template_mapper, validate_template, warn_and_drop_long_samples, warn_completion_is_not_empty, warn_duplicated_rows, warn_imbalanced_completion, warn_low_n_samples, warn_missing_suffix
label_desc: Use image node_id 18 for calling a global function with example usage: test_get_prepared_filename() without return types