@Override
  public IConfigMNode getChild(String name) {
    IConfigMNode child = null;
    if (children != null) {
      child = children.get(name);
    }
    return child;
  }
get the child with the name
iotdb-core/confignode/src/main/java/org/apache/iotdb/confignode/persistence/schema/mnode/impl/ConfigBasicInternalMNode.java