docs: def watch(self, limit=None, timeout=None):
          """Block method to watch the clipboard changing."""
          start_time = time.time()
          count = 0
          while not timeout or time.time() - start_time < timeout:
              new = self.read()
              if new != self.temp:
                  count += 1
                  self.callback(new)
                  if count == limit:
                      break
              self.temp = new
              time.sleep(self.interval)