code: @Override
      public void appendXMLToMasterStyle(final XMLUtil util, final Appendable appendable) throws IOException {
          if (this.centerRegion != null && !this.centerRegion.isEmpty())
              this.centerRegion.appendXMLContent(util, appendable);
      }
docs: Used in file styles.xml, in <office:master-styles>,<style:master-page />.
  
  @throws IOException If an I/O error occurs