def writeExtras(self):
        """
        Write out completion information for extra arguments appearing on the
        command-line. These are extra positional arguments not associated
        with a named option. That is, the stuff that gets passed to
        Options.parseArgs().

        @return: L{None}

        @raises: ValueError: if C{Completer} with C{repeat=True} is found and
            is not the last item in the C{extraActions} list.
        """
        for i, action in enumerate(self.extraActions):
            # a repeatable action must be the last action in the list
            if action._repeat and i != len(self.extraActions) - 1:
                raise ValueError("Completer with repeat=True must be "
                                 "last item in Options.extraActions")
            self.file.write(
                escape(action._shellCode('', usage._ZSH)).encode('utf-8'))
            self.file.write(b' \\\n')

        Write out completion information for extra arguments appearing on the
        command-line. These are extra positional arguments not associated
        with a named option. That is, the stuff that gets passed to
        Options.parseArgs().

        @return: L{None}

        @raises: ValueError: if C{Completer} with C{repeat=True} is found and
            is not the last item in the C{extraActions} list.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/python/_shellcomp.py