def _shellCode(self, optName, shellType):
        """
        Fetch a fragment of shell code representing this action which is
        suitable for use by the completion system in _shellcomp.py

        @type optName: C{str}
        @param optName: The long name of the option this action is being
            used for.

        @type shellType: C{str}
        @param shellType: One of the supported shell constants e.g.
            C{twisted.python.usage._ZSH}
        """
        if shellType == _ZSH:
            return "%s:%s:" % (self._repeatFlag,
                               self._description(optName))
        raise NotImplementedError("Unknown shellType %r" % (shellType,))

        Fetch a fragment of shell code representing this action which is
        suitable for use by the completion system in _shellcomp.py

        @type optName: C{str}
        @param optName: The long name of the option this action is being
            used for.

        @type shellType: C{str}
        @param shellType: One of the supported shell constants e.g.
            C{twisted.python.usage._ZSH}
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/python/usage.py