code: def test_sign():
      fun = lambda x: 3.0 * np.sign(x)
      check_grads(fun)(1.1)
      check_grads(fun)(-1.1)
  
imports: from __future__ import absolute_import
  import autograd.numpy
  import autograd.numpy.random
  from autograd.test_util import check_grads
  from autograd import grad
label_desc: Use image node_id 3 for calling a global function with example usage: test_sign() without return types