@Override
  public ICachedMNode getChild(String name) {
    ICachedMNode child = null;
    if (children != null) {
      child = children.get(name);
    }
    if (child == null && deviceInfo != null) {
      child = deviceInfo.getAliasChild(name);
    }
    return child;
  }
get the child with the name
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/schemaengine/schemaregion/mtree/impl/pbtree/mnode/impl/CachedBasicInternalMNode.java