Set Fixed ANTsImage Mask for metric

def set_fixed_mask(self, image):
        """
        Set Fixed ANTsImage Mask for metric
        """
        if not isinstance(image, iio.ANTsImage):
            raise ValueError('image must be ANTsImage type')

        if image.dimension != self.dimension:
            raise ValueError('image dim (%i) does not match metric dim (%i)' % (image.dimension, self.dimension))

        self._metric.setFixedImage(image.pointer, True)
        self.fixed_mask = image