<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _checksum(self, msg):
 """ Calculate the checksum of a packet. This is inspired by a response on StackOverflow here: https://stackoverflow.com/a/1769267/7242672 Thank you to StackOverflow user Jason Orendorff. """

        def carry_around_add(a, b):
            c = a + b
            return (c & 0xffff) + (c >> 16)

        s = 0
        for i in range(0, len(msg), 2):
            w = (msg[i] << 8) + msg[i + 1]
            s = carry_around_add(s, w)
        s = ~s & 0xffff

        return s