code: def testGraphModeEagerGradError(self):
      with context.graph_mode():
  
          def f():
              x = variable_scope.get_variable(
                  "v", initializer=constant_op.constant(1.0)
              )
              return x * constant_op.constant(2.0)
  
          with self.assertRaisesRegex(
              ValueError, "No trainable variables were accessed"
          ):
              backprop.implicit_val_and_grad(f)()
  
imports: from absl.testing import parameterized
  from tensorflow.python.eager import backprop
  from tensorflow.python.eager import context
  from tensorflow.python.eager.polymorphic_function import polymorphic_function
  from tensorflow.python.framework import config
  from tensorflow.python.framework import constant_op
  from tensorflow.python.framework import dtypes
  from tensorflow.python.framework import indexed_slices
  from tensorflow.python.framework import ops
  from tensorflow.python.framework import tensor_shape
  from tensorflow.python.framework import test_util
  from tensorflow.python.ops import array_ops
  from tensorflow.python.ops import cond
  from tensorflow.python.ops import gradients_impl
  from tensorflow.python.ops import math_ops
  from tensorflow.python.ops import nn_grad
  from tensorflow.python.ops import nn_ops
  from tensorflow.python.ops import resource_variable_ops
  from tensorflow.python.ops import variable_scope
  from tensorflow.python.ops import variables
  from tensorflow.python.ops import while_loop
  from tensorflow.python.platform import test
label_desc: Use image node_id 21 for calling the FunctionGradientsTest obj's underlying member method code with example usage: obj.testGraphModeEagerGradError() and returns: unknown