Calculates the checksum char used for the 16th char.
    Author: Vincenzo Palazzo

def checksum(value):
    """
    Calculates the checksum char used for the 16th char.
    Author: Vincenzo Palazzo
    """
    return chr(65 + sum(CHECKSUM_TABLE[index % 2][ALPHANUMERICS_DICT[char]]
                        for index, char in enumerate(value)) % 26)