docs: private void precheckStateAllNull() throws IllegalStateException {
          if ((doubleValue != null) || (doubleArray != null)
              || (longValue != null) || (longArray != null)
              || (stringValue != null) || (stringArray != null)
              || (map != null)) {
              throw new IllegalStateException("Expected all properties to be empty: " + this);
          }
      }