Return options already used in the
        command line

        rtype: command.Option generator

def used_options(self):
        """Return options already used in the
        command line

        rtype: command.Option generator
        """
        for option_str in filter(lambda c: c.startswith('-'), self.words):
            for option in list(self.cmd.options.values()):
                if option_str in option.option_strings:
                    yield option