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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 packed_checksum(self, data):
 """Given the data of the entire packet return the checksum bytes"""

        self.field.setval(self.algo(data[self.start:self.end]))
        sio = BytesIO()
        self.field.pack(sio)
        return sio.getvalue()