protected void sinkHeader(Sink sink, String header) {
   sink.tableHeaderCell();
   if (header != null && header.length() > 0) {
     sink.text(header);
   } else {
     sink.nonBreakingSpace();
   }
   sink.tableHeaderCell_();
 }
 protected void tableHeaderCell_(Sink sink) {
   sink.tableHeaderCell_();
 }