code: def periodic_service_rpcs(self):
          
  
          to_remove = []
  
          now = monotonic()
          for rpc_tag, rpc in self.in_flight_rpcs.items():
              expiry = rpc.sent_timestamp + rpc.timeout
              if now > expiry:
                  to_remove.append(rpc_tag)
  
          for tag in to_remove:
              del self.in_flight_rpcs[tag]
docs: Check if any RPC has expired and remove it from the in flight list.
  
          This function should be called periodically to expire any RPCs that never complete.