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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 upgrade(self, flag):
 """Upgrade Slackware binary packages with new """

        for pkg in self.binary:
            try:
                subprocess.call("upgradepkg {0} {1}".format(flag, pkg),
                                shell=True)
                check = pkg[:-4].split("/")[-1]
                if os.path.isfile(self.meta.pkg_path + check):
                    print("Completed!\n")
                else:
                    raise SystemExit()
            except subprocess.CalledProcessError:
                self._not_found("Can't upgrade", self.binary, pkg)
                raise SystemExit(1)