code: def test_grad():
      op = SymPyCCode([xs], xs**2)
      zt = op(xt)
      ztprime = theano.grad(zt, xt)
      assert ztprime.owner.op.expr == 2 * xs
  
imports: from __future__ import absolute_import, print_function, division
  import theano
  from theano.scalar.basic_sympy import SymPyCCode
  from theano.scalar.basic import floats
  from nose.plugins.skip import SkipTest
label_desc: Use image node_id 2 for calling a global function with example usage: test_grad() without return types