def _make_legend_dataset(
        df, date_column, normal_columns, stands_out_columns):
    """
    Make a data set for the legend.

    Parameters
    ----------
    df : pandas.DataFrame
        Data frame to be plotted. A date column is required.
    date_column : str
        Column name of the date in the data frame.
    normal_columns : list of str
        A list of the column names of targets for which inconspicuous
        colors are set.
    stands_out_columns : list of str
        A list of column names for which prominent colors are set.

    Returns
    -------
    legend_dataset : list of dicts
        A list of dictionaries containing data for the legend.
        The following keys are set in the dictionary.
        - key : str -> Column names excluding dates are set.
        - value : The value of the last date is set.
    """
    df.sort_values(by=date_column, inplace=True)
    df.reset_index(drop=True, inplace=True)
    df_len = len(df)
    legend_dataset = []
    merged_columns = [*normal_columns, *stands_out_columns]
    for column_name in merged_columns:
        last_date_val = df.loc[df_len - 1, column_name]
        legend_dataset.append({
            'key': column_name,
            'value': last_date_val,
        })
    return legend_dataset