input: 
  class FileSystem(object):
  	def __init__(self, param):
  		self.__jsub_dir = os.path.expanduser(param.get('taskDir', '~/jsub/'))
  		self.__logger = logging.getLogger('JSUB')
  		self.__json_format = param.get('format', 'compact')
  
  	def save_task(self, data):
  		if 'id' not in data:
  			safe_mkdir(self.__jsub_dir)
  			data['id'] = self.__new_task_id()
  		safe_mkdir(os.path.join(self.__jsub_dir,str(data['id']),'taskInfo'))
  		task_path = os.path.join(self.__jsub_dir, str(data['id']),'taskInfo','repo')
  
  		data_str = self.__json_str(data)
  		with open(task_path, 'a+') as f:
  			fcntl.flock(f, fcntl.LOCK_EX)
  			f.seek(0)
  			f.truncate()
  			f.write(data_str)
  
  	def delete_task(self, task_id):
  		safe_rmdir(os.path.join(self.__jsub_dir,str(task_id)))
  
  	def find_by_id(self, task_id):
  		return self.task_data(task_id)
  
  	def find_by_ids(self, task_ids):
  		all_data = []
  		for task_id in task_ids:
  			try:
  				td = self.task_data(task_id)
  				all_data.append(td)
  			except RepoReadError as e:
  				self.__logger.debug(e)
  		return all_data
  
  	def all_task_data(self, order='asc'):
  		task_ids =[d for d in os.listdir(self.__jsub_dir) if os.path.isdir(os.path.join(self.__jsub_dir,d))]
  		task_ids.sort(key=int, reverse=(order=='desc'))
  		return self.find_by_ids(task_ids)
  
  	def task_data(self, task_id):
  		safe_mkdir(os.path.join(self.__jsub_dir,str(task_id),'taskInfo'))
  		task_path = os.path.join(self.__jsub_dir,str(task_id),'taskInfo','repo')
  		with open(task_path, 'a+') as f:
  			fcntl.flock(f, fcntl.LOCK_EX)
  			f.seek(0)
  			data_str = f.read()
  
  		try:
  			return json.loads(data_str)
  		except ValueError as e:
  			raise RepoReadError('JSON decode error on task %s: %s' % (task_id, e))
  
  	def __new_task_id(self):
  		task_ids =[int(d) for d in os.listdir(self.__jsub_dir) if os.path.isdir(os.path.join(self.__jsub_dir,d))]
  		if not task_ids:
  			return 1
  		task_ids.sort(key=int, reverse=True)
  		return(task_ids[0]+1)
  
  	def __json_str(self, data):
  		if self.__json_format == 'pretty':
  			return json.dumps(data, indent=2)
  		return json.dumps(data, separators=(',', ':'))
  
  
output:     
      def update_task(self, task_id, new_data):
          task_path = os.path.join(self.__jsub_dir, str(task_id), 'taskInfo', 'repo')
          with open(task_path, 'a+') as f:
              fcntl.flock(f, fcntl.LOCK_EX)
              f.seek(0)
              data_str = f.read()
              try:
                  data = json.loads(data_str)
                  data.update(new_data)
                  f.truncate()
                  f.write(self.__json_str(data))
              except ValueError as e:
                  raise RepoReadError('JSON decode error on task %s: %s' % (task_id, e))
  
      def list_tasks(self, order='asc'):
          task_ids = [d for d in os.listdir(self.__jsub_dir) if os.path.isdir(os.path.join(self.__jsub_dir, d))]
          task_ids.sort(key=int, reverse=(order == 'desc'))
          return task_ids
  
      def clear_all_tasks(self):
          for task_id in os.listdir(self.__jsub_dir):
              if os.path.isdir(os.path.join(self.__jsub_dir, task_id)):
                  self.delete_task(task_id)
  