code: def test_merge(self):
      raise SkipTest("Optimization temporarily disabled")
      x = tensor.vector("x")
      y = tensor.vector("y")
      c = tensor.iscalar("c")
      z1 = ifelse(c, x + 1, y + 1)
      z2 = ifelse(c, x + 2, y + 2)
      z = z1 + z2
      f = theano.function([c, x, y], z)
      assert (
          len(
              [
                  n
                  for n in f.maker.fgraph.toposort()
                  if isinstance(n.op, IfElse)
              ]
          )
          == 1
      )
  
imports: from __future__ import absolute_import, print_function, division
  import unittest
  import numpy
  from nose.plugins.skip import SkipTest
  from six.moves import reduce
  import theano
  from theano import tensor
  import theano.ifelse
  from theano.ifelse import IfElse, ifelse
  from theano.tests import unittest_tools
label_desc: Use image node_id 15 for calling the test_ifelse obj's underlying member method code with example usage: obj.test_merge() without return types