code: def test_grad_identity():
      fun = lambda x: x
      df = grad(fun)
      ddf = grad(df)
      assert np.allclose(df(2.0), 1.0)
      assert np.allclose(ddf(2.0), 0.0)
  
imports: from __future__ import absolute_import
  import autograd.numpy
  import autograd.numpy.random
  from autograd.test_util import check_grads
  from autograd import grad
  import warnings
  import pytest
label_desc: Use image node_id 3 for calling a global function with example usage: test_grad_identity() without return types