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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _calculate_checksum(value):
 """4.12 Checksum Calculation from an unsigned short input"""

        # CRC
        polynomial = 0x131  # //P(x)=x^8+x^5+x^4+1 = 100110001
        crc = 0xFF

        # calculates 8-Bit checksum with given polynomial
        for byteCtr in [ord(x) for x in struct.pack(">H", value)]:
            crc ^= byteCtr
            for bit in range(8, 0, -1):
                if crc & 0x80:
                    crc = (crc << 1) ^ polynomial
                else:
                    crc = (crc << 1)
        return crc