code: void writeProcessingInstruction(final Writer output, final String name, final String value)
              throws SAXException {
          try {
              output.write(LESS_THAN);
              output.write(QUESTION);
              output.write(name);
              if (value != null) {
                  output.write(STRING_BLANK);
                  output.write(value);
              }
              output.write(QUESTION);
              output.write(GREATER_THAN);
          } catch (IOException e) {
              throw new SAXException(e);
          }
      }
docs: Convenience method to write a processing instruction.
  
  @param name  PI name
  @param value PI value, may be {@code null}