docs: def grow(self, amount):
          """Spawn new worker threads (not above self.max)."""
          for i in range(amount):
              if self.max > 0 and len(self._threads) >= self.max:
                  break
              worker = WorkerThread(self.server)
              worker.setName("CP Server " + worker.getName())
              self._threads.append(worker)
              worker.start()