def addoption(self, *opts: str, **attrs: Any) -> None:
        """Add an option to this group.

        If a shortened version of a long option is specified, it will
        be suppressed in the help. ``addoption('--twowords', '--two-words')``
        results in help showing ``--two-words`` only, but ``--twowords`` gets
        accepted **and** the automatic destination is in ``args.twowords``.

        :param opts:
            Option names, can be short or long options.
        :param attrs:
            Same attributes as the argparse library's :meth:`add_argument()
            <argparse.ArgumentParser.add_argument>` function accepts.
        """
        conflict = set(opts).intersection(
            name for opt in self.options for name in opt.names()
        )
        if conflict:
            raise ValueError(f"option names {conflict} already added")
        option = Argument(*opts, **attrs)
        self._addoption_instance(option, shortupper=False)
Add an option to this group.

        If a shortened version of a long option is specified, it will
        be suppressed in the help. ``addoption('--twowords', '--two-words')``
        results in help showing ``--two-words`` only, but ``--twowords`` gets
        accepted **and** the automatic destination is in ``args.twowords``.

        :param opts:
            Option names, can be short or long options.
        :param attrs:
            Same attributes as the argparse library's :meth:`add_argument()
            <argparse.ArgumentParser.add_argument>` function accepts.
        
src/_pytest/config/argparsing.py