code: public void writePostamble(final XMLUtil util, final ZipUTF8Writer writer) throws IOException {
          if (this.autofilters != null) this.appendAutofilters(writer, util);
          writer.write("</office:spreadsheet>");
          writer.write("</office:body>");
          writer.write("</office:document-content>");
          writer.flush();
          writer.closeEntry();
      }
docs: Write the postamble into the given writer. Used by the FinalizeFlusher and by standard write method
  
  @param util   an XML util
  @param writer the destination
  @throws IOException if the postamble could not be written