old_contents: # -*- coding: utf-8 -*-
  
  try:
      import anydbm as dbm
      assert dbm
  except ImportError:
      import dbm
  
  from werobot.session import SessionStorage
  from werobot.utils import json_loads, json_dumps
  
  
  class FileStorage(SessionStorage):
      """
      FileStorage 会把你的 Session 数据以 dbm 形式储存在文件中。
  
      :param filename: 文件名， 默认为 ``werobot_session``
      """
      def __init__(self, filename='werobot_session'):
          self.db = dbm.open(filename, "c")
  
      def get(self, id):
          session_json = self.db.get(id, "{}")
          return json_loads(session_json)
  
      def set(self, id, value):
          self.db[id] = json_dumps(value)
  
      def delete(self, id):
          del self.db[id]
  
new_contents: # -*- coding: utf-8 -*-
  
  try:
      import anydbm as dbm
      assert dbm
  except ImportError:
      import dbm
  
  from werobot.session import SessionStorage
  from werobot.utils import json_loads, json_dumps
  
  
  class FileStorage(SessionStorage):
      """
      FileStorage 会把你的 Session 数据以 dbm 形式储存在文件中。
  
      :param filename: 文件名， 默认为 ``werobot_session``
      """
      def __init__(self, filename='werobot_session'):
          self.db = dbm.open(filename, "c")
  
      def get(self, id):
          try:
              session_json = self.db["id"]
          except KeyError:
              session_json = "{}"
          return json_loads(session_json)
  
      def set(self, id, value):
          self.db[id] = json_dumps(value)
  
      def delete(self, id):
          del self.db[id]
  
subject: Fix FileStorage's bug