@Override
  public IConfigMNode addChild(IConfigMNode parent, String childName, IConfigMNode child) {
    return parent.addChild(childName, child);
  }
This is a memory-based implementation of IMTreeStore. All MNodes are stored in memory.
iotdb-core/confignode/src/main/java/org/apache/iotdb/confignode/persistence/schema/ConfigMTreeStore.java