code: def test_clone_optimizer_from_string():
      clone = clone_optimizer("sgd")
      assert isinstance(clone, SGD)
  
file_path: keras-rl/tests/rl/test_util.py
imports: from __future__ import division
  import pytest
  import numpy
  from numpy.testing import assert_allclose
  from keras.models import Model, Sequential
  from keras.layers import Input, Dense, Concatenate
  from keras.optimizers import SGD
  import keras.backend
  from rl.util import clone_optimizer, clone_model, huber_loss, WhiteningNormalizer
label_desc: Use image node_id 4 for calling a global function with example usage: test_clone_optimizer_from_string() without return types