def coord(self):
        """Get 3D coordinate.

        Returns:
            numpy.array[3, N]: coordinate matrix

        """
        if not self.require_3D:
            self.fail(AttributeError("use 3D coordinate in 2D descriptor"))

        return self._context.get_coord(self)
Get 3D coordinate.

        Returns:
            numpy.array[3, N]: coordinate matrix