def opt_pyzone(self, filename):
        """Specify the filename of a Python syntax zone definition"""
        if not os.path.exists(filename):
            raise usage.UsageError(filename + ": No such file")
        self.zonefiles.append(filename)
Specify the filename of a Python syntax zone definition
stackoverflow/venv/lib/python3.6/site-packages/twisted/names/tap.py