async def get_options(self) -> List[Tuple[str, str]]:
        """Return list of possible values to select from."""
        options = [
            ("TRUE", "true"),
            ("FALSE", "false"),
        ]
        if self.context.get("null"):
            options.insert(0, ("", ""))

        return options
Return list of possible values to select from.
fastapi_admin/widgets/filters.py