docs: private void beforeName() throws IOException {
      int context = peek();
      if (context == NONEMPTY_OBJECT) { // first in object
        out.write(',');
      } else if (context != EMPTY_OBJECT) { // not in an object!
        throw new IllegalStateException("Nesting problem.");
      }
      newline();
      replaceTop(DANGLING_NAME);
    }