code: def loop(self, sleep_time=1, callback=None):
          
  
          self.log("No supported libraries found: using polling-method.")
          self._running = True
          self.trigger_init()
          self._scan(trigger=False)  # put after the trigger
          if self._warn:
              print("""
  You should install a third-party library so I don't eat CPU.
  Supported libraries are:
    - pyinotify (Linux)
    - pywin32 (Windows)
    - MacFSEvents (OSX)
  
  Use pip or easy_install and install one of those libraries above.
  """)
          while self._running:
              self._scan()
              if isinstance(callback, collections.Callable):
                  callback()
              time.sleep(sleep_time)
docs: Goes into a blocking IO loop. If polling is used, the sleep_time is
          the interval, in seconds, between polls.