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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 if_all_installed(self):
 """Check if all packages is already installed """

        count_inst = 0
        for inst in (self.dep_install + self.install):
            if (os.path.isfile(self.meta.pkg_path + inst[:-4]) and
                    "--download-only" not in self.flag):
                count_inst += 1
        if (count_inst == len(self.dep_install + self.install) and
                "--reinstall" not in self.flag):
            raise SystemExit()