old_contents: import rx
  import concurrent.futures
  import time
  
  seconds = [5, 1, 2, 4, 3]
  
  
  def sleep(t):
      time.sleep(t)
      return t
  
  
  def output(result):
      print '%d seconds' % result
  
  with concurrent.futures.ProcessPoolExecutor(5) as executor:
      rx.Observable.from_(seconds).flat_map(
          lambda s: executor.submit(sleep, s)
      ).subscribe(output)
  
  # 1 seconds
  # 2 seconds
  # 3 seconds
  # 4 seconds
  # 5 seconds
  
new_contents: from __future__ import print_function
  
  import rx
  import concurrent.futures
  import time
  
  seconds = [5, 1, 2, 4, 3]
  
  
  def sleep(t):
      time.sleep(t)
      return t
  
  
  def output(result):
      print('%d seconds' % result)
  
  with concurrent.futures.ProcessPoolExecutor(5) as executor:
      rx.Observable.from_(seconds).flat_map(
          lambda s: executor.submit(sleep, s)
      ).subscribe(output)
  
  # 1 seconds
  # 2 seconds
  # 3 seconds
  # 4 seconds
  # 5 seconds
  
subject: Fix parallel example for Python 3