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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 cmd(self, argv):
 """Run one command and exit. "argv" is the arglist for the command to run. argv[0] is the command to run. If argv is an empty list then the 'emptyline' handler is run. Returns the return value from the command handler. """

        assert isinstance(argv, (list, tuple)), \
                "'argv' is not a sequence: %r" % argv
        retval = None
        try:
            argv = self.precmd(argv)
            retval = self.onecmd(argv)
            self.postcmd(argv)
        except:
            if not self.cmdexc(argv):
                raise
            retval = 1
        return retval