code: def test_warn_missing_suffix():
      df_no_common = pd.DataFrame(
          {
              "prompt": [f"prompt{i}" for i in range(100)],
              "completion": [f"completion{i}" for i in range(100)],
          }
      )
      message = f"TODO: prompt does not have common suffix, please add one (e.g. \\n) at the end of prompt_template\n"
      message += f"TODO: completion does not have common suffix, please add one (e.g. \\n) at the end of completion_template\n"
  
      assert warn_missing_suffix(df_no_common) == message
      df_common = pd.DataFrame(
          {
              "prompt": [f"prompt{i} answer:" for i in range(100)],
              "completion": [f"completion{i}\n" for i in range(100)],
          }
      )
      assert warn_missing_suffix(df_common) is 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 5 for calling a global function with example usage: test_warn_missing_suffix() without return types