content: from pyrsistent import immutable
  
  
  class Monitor(immutable('sender', name='_Monitor')):
      pass
  
  
  class Unmonitor(immutable('sender', name='_Unmonitor')):
      pass
  
  
  class Cancel(immutable('sender', name='_Cancel')):
      pass
  
  
  class Kill(immutable('sender', name='_Kill')):
      pass
  
  
  class Fork(immutable('sender, func, args, kwargs', name='_Fork')):
      pass
  
  
  class ForkWithMonitor(immutable('sender, func, args, kwargs', name='_ForkWithMonitor')):
      pass
  
  
  class ForkResponse(immutable('new_actor ', name='_ForkResponse')):
      pass
  
  
  class Down(immutable('sender, reason', name='_OkMessage')):
      pass
  