def update_font_references(modified_font)
      xf = workbook.register_new_font(modified_font, get_cell_xf)
      self.style_index = workbook.register_new_xf(xf)
    end
def update_font_references(modified_font)
      xf = workbook.register_new_font(modified_font, get_cell_xf)
      self.style_index = workbook.register_new_xf(xf)
    end
Helper method to update the font array and xf array