def area_covered_national(record: dict):
    """
    Function to remove area_covered == "national"

    Replace with None.

    Parameters
    ----------
    record : dict
        Input record.

    Returns
    -------
    type
        Record with `area_covered` changed.

    """

    if record['area_covered'] in ['national']:

        record['area_covered'] = None

    return(record)