@ApiStatus.Internal
  public void addChild(@NotNull StructureViewTreeElement childElement) {
    if (mySubRegions != null) {
      for (CustomRegionTreeElement subRegion : mySubRegions) {
        if (subRegion.containsElement(childElement)) {
          subRegion.addChild(childElement);
          return;
        }
      }
    }
    myChildElements.add(childElement);
  }
@ApiStatus.Internal
  public void addChild(@NotNull StructureViewTreeElement childElement)