code: def cleanup_candidates(self, node_ip):
          
          if node_ip in self.factory.candidates:
              old_candidates = []
              for candidate in self.factory.candidates[node_ip]:
                  elapsed = int(time.time() - candidate["time"])
                  if elapsed > self.challege_timeout:
                      old_candidates.append(candidate)
  
              for candidate in old_candidates:
                  self.factory.candidates[node_ip].remove(candidate)
docs: Removes old TCP hole punching candidates for a
          designated node if a certain amount of time has passed
          since they last connected.