@classmethod
def from_image_ref(cls, context, image_api, image_ref):
    """Create instance from glance image

        :param context: the request context
        :param image_api: the glance client API
        :param image_ref: the glance image identifier

        Creates a new object instance, initializing from the
        properties associated with a glance image

        :returns: an ImageMeta instance
        """
    image_meta = image_api.get(context, image_ref)
    image = cls.from_dict(image_meta)
    setattr(image, 'id', image_ref)
    return image
