code: def test_stack_fallback(self):
      def dummy_function(l):
          # Lazy person's mock: just transform the argument in a way in which we
          # can check that this function was indeed called.
          return [x * 2 for x in l]
  
      opts = data_structures.ListStackOpts(
          element_dtype=None, original_call=dummy_function
      )
  
      self.assertAllEqual(
          data_structures.list_stack([1, 2], opts), [2, 4]
      )
  
imports: from tensorflow.python.autograph.operators import data_structures
  from tensorflow.python.framework import constant_op
  from tensorflow.python.framework import dtypes
  from tensorflow.python.framework import tensor
  from tensorflow.python.framework import test_util
  from tensorflow.python.ops import list_ops
  from tensorflow.python.ops import tensor_array_ops
  from tensorflow.python.platform import test
label_desc: Use image node_id 16 for calling the ListTest obj's underlying member method code with example usage: obj.test_stack_fallback() and returns: unknown