code: protected boolean tryToAddIntoContainer(IAsmElementUmlInteractive<?, ?, ?, ?> asmElm, int screenX, int screenY) {
      IAsmElementUmlInteractive<? extends ContainerFull<?>, ?, ?, ?> container = findContainerAtExcept(screenX, screenY, asmElm.getElementUml().getId());
      if(container != null) {
        container.getElementUml().getElements().add(asmElm);
        return true;
      }
      return false;
    }
docs: Utils: