'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'

@classmethod
def from_image_ref(cls, context, image_api, image_ref):

    image_meta = image_api.get(context, image_ref)
    image = cls.from_dict(image_meta)
    setattr(image, 'id', image_ref)
    return image
