code: def test_wrt_tensor_is_None(model_and_losses):
      model, losses = model_and_losses
      opt = Optimizer(model.input, losses, wrt_tensor=None)
      opt.minimize()
  
      assert opt.wrt_tensor_is_input_tensor
      assert opt.wrt_tensor is not None
      assert opt.wrt_tensor != opt.input_tensor
  
file_path: keras-vis/tests/vis/test_optimizer.py
imports: import pytest
  import keras.backend
  from keras.layers import Dense
  from keras.models import Sequential
  from vis.optimizer import Optimizer
  from vis.losses import Loss
label_desc: Use image node_id 2 for calling a global function with example usage: test_wrt_tensor_is_None(model_and_losses) without return types