import tensorflow as tf

                        else self.config['eval_batch_size']
                shards = {d: tf.unstack(v, num=batch_size*self.n_gpus, axis=0)
                          for d, v in data.items()}
                shards = [{d: tf.stack(v[i::self.n_gpus]) for d, v in shards.items()}
                          for i in range(self.n_gpus)]

