@Override
  protected Iterator<N> getChildrenIterator(N parent) throws MetadataException {
    if (parent.isAboveDatabase()) {
      return new MNodeIterator<>(parent.getChildren().values().iterator());
    } else {
      return store.getTraverserIterator(parent, templateMap, skipPreDeletedSchema);
    }
  }
The interface to start the traversal. The node process should be defined before traversal by
overriding or implement concerned methods.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/schemaengine/schemaregion/mtree/traverser/Traverser.java