old_contents: import kaa
  
  @kaa.yield_execution(synchronize = True)
  def f(x):
      print 'in', x
      yield kaa.YieldContinue
      print 'work1', x
      yield kaa.YieldContinue
      print 'work2', x
      yield kaa.YieldContinue
      print 'out', x
      
  f(1)
  f(2)
  f(3)
  kaa.main.run()
  
new_contents: import kaa
  
  @kaa.coroutine(synchronize = True)
  def f(x):
      print 'in', x
      yield kaa.YieldContinue
      print 'work1', x
      yield kaa.YieldContinue
      print 'work2', x
      yield kaa.YieldContinue
      print 'out', x
      
  f(1)
  f(2)
  f(3)
  kaa.main.run()
  
subject: rename yield_execution to coroutine