def orders_by_hours(data_frame):
    """ Gives orders_count by hour of the days.

    :param data_frame: DataFrame containing orders data.
    :return: DataFrame of order_ids count by hour of the days.
    """
    grouped = data_frame.groupby(['order_hour_of_day'], as_index=False)
    count = grouped.agg({'order_id': 'count'}).rename(
        columns={'order_id': 'order_id_count'})
    return count