def _line_spacing(spacing_line, spacing_lineRule):
        """
        Return the line spacing value calculated from the combination of
        *spacing_line* and *spacing_lineRule*. Returns a |float| number of
        lines when *spacing_lineRule* is ``WD_LINE_SPACING.MULTIPLE``,
        otherwise a |Length| object of absolute line height is returned.
        Returns |None| when *spacing_line* is |None|.
        """
        if spacing_line is None:
            return None
        if spacing_lineRule == WD_LINE_SPACING.MULTIPLE:
            return spacing_line / Pt(12)
        return spacing_line