@classmethod
def update_all(cls, image):
    """
        Method updating all real classes inherited from ImageRelatedMixin
        Used when an image is updated: each instance should be updated as ref_image and ref_alt are denormalized from image

        Args:
            image (stack_it.Image instance): All related "ImageRelatedMixin" related to this instance will be updated
        """
    subclasses = cls.__subclasses__()
    for cl in subclasses:
        if cl._meta.abstract:
            cl.update_all(image)
        else:
            cl.objects.filter(image=image).update(ref_image=image.image,
                ref_alt=image.alt)
