@Override
      public N next() {
        if (!hasNext()) {
          throw new NoSuchElementException();
        }
        N result = next;
        next = null;
        return result;
      }
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