@staticmethod
def _get_checksum(data):
    """
        Calculates the modulo 256 checksum of a string of characters.
        This checksum, expressed in hexadecimal, is used in every
        communication of this instrument, as a sanity check.

        Returns a string corresponding to the hexademical value
        of the checksum, without the `0x` prefix.

        :param data: Byte string to be checksummed
        :type: `str`

        :rtype: `str`
        """
    chrs = list(data)
    total = 0
    for c in chrs:
        total += ord(c)
    return format(total % 256, '02X')
