code: public JSONWriter perOperationInstance(int features, JsonGenerator g)
      {
          if (getClass() != JSONWriter.class) { // sanity check
              throw new IllegalStateException("Sub-classes MUST override perOperationInstance(...)");
          }
          return new JSONWriter(this, features,
                  _writerLocator.perOperationInstance(this, features), g);
      }
docs: /*
  ********************************************************************
  /* New instance creation
  ********************************************************************