Sanity checks on the image data

def _check_image(self, image_nD):
        """Sanity checks on the image data"""

        self.input_image = load_image_from_disk(image_nD)

        if len(self.input_image.shape) < 3:
            raise ValueError('Input image must be atleast 3D')

        if np.count_nonzero(self.input_image) == 0:
            raise ValueError('Input image is completely filled with zeros! '
                             'Must be non-empty')