Returns the contained value or computes it from ``callback``.

        Args:
            callback: The the default callback.

        Returns:
            The contained value if the :py:class:`Option` is ``Some``,
            otherwise ``callback()``.

        Examples:
            >>> Some(0).unwrap_or_else(lambda: 111)
            0
            >>> NONE.unwrap_or_else(lambda: 'ha')
            'ha'

def unwrap_or_else(self, callback: Callable[[], U]) -> Union[T, U]:
        """
        Returns the contained value or computes it from ``callback``.

        Args:
            callback: The the default callback.

        Returns:
            The contained value if the :py:class:`Option` is ``Some``,
            otherwise ``callback()``.

        Examples:
            >>> Some(0).unwrap_or_else(lambda: 111)
            0
            >>> NONE.unwrap_or_else(lambda: 'ha')
            'ha'
        """
        return self._val if self._is_some else callback()