old_contents: import base64
  import ipaddress
  import struct
  
  from .memory import MemorySession
  from ..crypto import AuthKey
  
  CURRENT_VERSION = '1'
  
  
  class StringSession(MemorySession):
      """
      This minimal session file can be easily saved and loaded as a string.
  
      It is thought to be used where you don't want to create any on-disk
      files but would still like to be able to save and load existing sessions
      by other means.
      """
      def __init__(self, string=None):
          super().__init__()
          if string and string[0] != CURRENT_VERSION:
              raise ValueError('Not a valid string')
  
          ip_len = 4 if len(string) == 353 else 16
          self._dc_id, ip, self._port, key = struct.unpack(
              '>B{}sH256s'.format(ip_len), base64.urlsafe_b64decode(string[1:]))
  
          self._server_address = ipaddress.ip_address(ip).compressed
          if any(key):
              self._auth_key = AuthKey(key)
  
      def save(self):
          if not self._auth_key:
              return ''
  
          ip = ipaddress.ip_address(self._server_address).packed
          return CURRENT_VERSION + base64.urlsafe_b64encode(struct.pack(
              '>B{}sH256s'.format(len(ip)),
              self._dc_id,
              ip,
              self._port,
              self._auth_key.key
          )).decode('ascii')
  
new_contents: import base64
  import ipaddress
  import struct
  
  from .memory import MemorySession
  from ..crypto import AuthKey
  
  CURRENT_VERSION = '1'
  
  
  class StringSession(MemorySession):
      """
      This minimal session file can be easily saved and loaded as a string.
  
      It is thought to be used where you don't want to create any on-disk
      files but would still like to be able to save and load existing sessions
      by other means.
      """
      def __init__(self, string=None):
          super().__init__()
          if string:
              if string[0] != CURRENT_VERSION:
                  raise ValueError('Not a valid string')
  
              string = string[1:]
              ip_len = 4 if len(string) == 352 else 16
              self._dc_id, ip, self._port, key = struct.unpack(
                  '>B{}sH256s'.format(ip_len), base64.urlsafe_b64decode(string))
  
              self._server_address = ipaddress.ip_address(ip).compressed
              if any(key):
                  self._auth_key = AuthKey(key)
  
      def save(self):
          if not self._auth_key:
              return ''
  
          ip = ipaddress.ip_address(self._server_address).packed
          return CURRENT_VERSION + base64.urlsafe_b64encode(struct.pack(
              '>B{}sH256s'.format(len(ip)),
              self._dc_id,
              ip,
              self._port,
              self._auth_key.key
          )).decode('ascii')
  
subject: Fix StringSession(None)