/** {@inheritDoc} */
  @Override
  protected void checkCanFetch() {
    super.checkCanFetch();

    if (startNodeGraphId != NEW || endNodeGraphId != NEW) {
      throw new IllegalStateException("Must not specify start/end node for existing relationship!");
    }

    if (type != null) {
      throw new IllegalStateException("Must not specify type for existing relationship!");
    }
  }
  /** {@inheritDoc} */
  @Override
  protected void checkCanCreate() {
    super.checkCanCreate();

    if (type == null || type.length() == 0) {
      throw new IllegalStateException("Relationship type must not be null or empty");
    }

    if (startNodeGraphId == NEW || endNodeGraphId == NEW) {
      throw new IllegalStateException("Start and End node IDs must be specified");
    }
  }