'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}'

def _shellCode(self, optName, shellType):

    if (shellType == _ZSH):
        return ('%s:%s:' % (self._repeatFlag, self._description(optName)))
    raise NotImplementedError(('Unknown    shellType    %r' % (shellType,)))
