def rows_above_layout(self):
        """
        Return the number of rows visible in the terminal above the layout.
        """
        if self._in_alternate_screen:
            return 0
        elif self._min_available_height > 0:
            total_rows = self.output.get_size().rows
            last_screen_height = self._last_screen.height if self._last_screen else 0
            return total_rows - max(self._min_available_height, last_screen_height)
        else:
            raise HeightIsUnknownError('Rows above layout is unknown.')
Return the number of rows visible in the terminal above the layout.