code: public ParameterBuilder<T> property(String key, Object value) {
      if (key == null) {
        throw new IllegalArgumentException("Key argument must not be null.");
      }
      this.properties.put(key, value);
      return this;
    }
docs: Further property for documentation and configuration of behavior in configuration editor.
  @param key Property key
  @param value Property value
  @return this