code: def _removeOldBackRefs(senderkey, signal, receiver, receivers):
      
      try:
          index = receivers.index(receiver)
          # need to scan back references here and remove senderkey
      except ValueError:
          return False
      else:
          oldReceiver = receivers[index]
          del receivers[index]
          found = 0
          signals = connections.get(signal)
          if signals is not None:
              for sig,recs in connections.get(signal,{}).items():
                  if sig != signal:
                      for rec in recs:
                          if rec is oldReceiver:
                              found = 1
                              break
          if not found:
              _killBackref( oldReceiver, senderkey )
              return True
          return False
docs: Kill old sendersBack references from receiver
  
      This guards against multiple registration of the same
      receiver for a given signal and sender leaking memory
      as old back reference records build up.
  
      Also removes old receiver instance from receivers