code: def __live_receivers(signal):
      
      with __lock:
          __purge()
          receivers = [funcref() for funcref in __receivers[signal]]
  
      return receivers
docs: Return all signal handlers that are currently still alive for the
      input `signal`.
  
      Args:
          signal: A signal name.
  
      Returns:
          A list of callable receivers for the input signal.