code: @Override
      public void writeArrayValueSeparator(JsonGenerator jg)
          throws IOException, JsonGenerationException
      {
          jg.writeRaw(',');
          _arrayIndenter.writeIndentation(jg, _nesting);
      }
docs: Method called after an array value has been completely
  output, and before another value is to be output.
  <p>
  Default handling (without pretty-printing) will output a single
  comma to separate the two. Pretty-printer is
  to output a comma as well, but can surround that with other
  (white-space) decoration.