code: private void tab(Writer output, int delta) throws IOException
      {
          if (!isPrettyPrint)
          {
              return;
          }
          output.write(NEW_LINE);
          depth += delta;
          for (int i=0; i < depth; i++)
          {
              output.write("  ");
          }
      }
docs: tab the JSON output by the given number of characters specified by delta.
  @param output Writer being used for JSON outpt.
  @param delta int number of characters to tab.
  @throws IOException