remove File.replace_ext()

    def derive2(self, *args, **kwargs):

        return self.derive(*args, **kwargs, level=2)

    def replace_ext(

        self, new_ext: Optional[str] = "img.fits", new_dir: Optional[str] = None

    ) -> str:

        if new_dir is None:

            new_dir = self.new_dir

        if new_ext is None:

            new_ext = self.ext

        if new_ext.startswith("."):

            return os.path.join(new_dir, self.prefix + new_ext)

        else:

            return os.path.join(new_dir, self.prefix + "_" + new_ext)

    def __repr__(self):

        return f"<File {self.file_path}>"