public static RelationId of(Node sourceNode) {
    return new RelationId(Optional.of(NodeRef.of(sourceNode)));
  }
Creates {@link RelationId} equal to any {@link RelationId} created from exactly the same
source.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/relational/analyzer/RelationId.java