def map_or(self, callback: Callable[[T], U], default: A) -> Union[U, A]:
        """
        Applies the ``callback`` to the contained value or returns ``default``.

        Args:
            callback: The callback to apply to the contained value.
            default: The default value.

        Returns:
            The ``callback`` result if the contained value is ``Some``,
            otherwise ``default``.

        Notes:
            If you wish to use the result of a function call as ``default``,
            it is recommended to use :py:meth:`map_or_else` instead.

        Examples:
            >>> Some(0).map_or(lambda x: x + 1, 1000)
            1
            >>> NONE.map_or(lambda x: x * x, 1)
            1
        """
        return callback(self._val) if self._is_some else default