code: def test_split_into_train_validation():
      df = pd.DataFrame(
          {"prompt": ["a"] * 10, "completion": ["b"] * 10}
      )
      df_train, df_val = split_into_train_validation(
          df, val_proportion=0.1
      )
      assert len(df_train) == 9
      assert len(df_val) == 1
  
      df_train, df_val = split_into_train_validation(
          df, val_proportion=0.2
      )
      assert len(df_train) == 8
      assert len(df_val) == 2
  
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 19 for calling a global function with example usage: test_split_into_train_validation() without return types