code: def test_single_step(self):
      optimizer = AdamW(learning_rate=0.5)
      grads = ops.array([1.0, 6.0, 7.0, 2.0])
      vars = backend.Variable([1.0, 2.0, 3.0, 4.0])
      optimizer.apply_gradients(zip([grads], [vars]))
      self.assertAllClose(
          vars, [0.4980, 1.4960, 2.494, 3.492], rtol=1e-4, atol=1e-4
      )
  
file_path: keras/keras/optimizers/adamw_test.py
imports: import numpy
  from keras import backend
  from keras import ops
  from keras import testing
  from keras.optimizers.adamw import AdamW
label_desc: Use image node_id 2 for calling the AdamWTest obj's underlying member method code with example usage: obj.test_single_step() without return types