code: def test_l2(self):
      value = np.random.random((4, 4))
      x = backend.Variable(value)
      y = regularizers.L2(0.1)(x)
      self.assertAllClose(y, 0.1 * np.sum(np.square(value)))
  
imports: import numpy
  from keras import backend
  from keras import regularizers
  from keras import testing
  from keras.regularizers.regularizers import validate_float_arg
label_desc: Use image node_id 3 for calling the RegularizersTest obj's underlying member method code with example usage: obj.test_l2() without return types