Set spacing to *value* lines, e.g. 1.75 lines. A ./a:spcPts child is
        removed if present.

def set_spcPct(self, value):
        """
        Set spacing to *value* lines, e.g. 1.75 lines. A ./a:spcPts child is
        removed if present.
        """
        self._remove_spcPts()
        spcPct = self.get_or_add_spcPct()
        spcPct.val = value