def __new__(cls, *args, **kwargs) -> "GmshMesher":
        if cls._instance is not None:
            raise RuntimeError(
                "Multiple Delaunay2D instances are not allowed. "
                "Please use del statement to clean up before creating a new instance."
            )
        cls._instance = super().__new__(cls)
        cls._instance._initialized = True
        return cls._instance