def METHOD_NAME(self):
    ssim_list = []
    for (pred, target) in zip(self.preds, self.targets):
        ssim_list.append(self.SSIM(pred, target))
        self.FID(pred, target)
    ssim_list = torch_nested_numpify(ssim_list)
    fid = self.FID.get_value()
    return {MetricKeys.SSIM: np.mean(ssim_list), MetricKeys.FID: fid}