def block_date(cursor, imei_norm: str) -> str:
    """
    Method to get block date of an IMEI from Notification and Blacklist.

    Arguments:
        cursor: PostgreSQL database connection cursor object
        imei_norm: Normalized IMEI
    Returns:
        Block Date of the IMEI if exists otherwise None
    """
    # check if it is in blacklist
    cursor.execute("""SELECT MIN(block_date) AS block_date
                        FROM classification_state
                       WHERE imei_norm = %(imei_norm)s
                         AND virt_imei_shard = calc_virt_imei_shard(%(imei_norm)s)
                         AND end_date IS NULL""",
                   {'imei_norm': imei_norm})
    imei_block_date = cursor.fetchone()
    return imei_block_date.block_date