<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def start_watcher(self):
 """ Start the watcher thread that tries to upload usage statistics. """

        if self._watcher and self._watcher.is_alive:
            self._watcher_enabled = True
        else:
            logger.debug('Starting watcher.')
            self._watcher = threading.Thread(target=self._watcher_thread, name='usage_tracker')
            self._watcher.setDaemon(True)
            self._watcher_enabled = True
            self._watcher.start()