def __init__(self, **settings):
super(FileSession, self).__init__(**settings)<EOL>self.host = settings.get("<STR_LIT:host>", self.DEFAULT_SESSION_POSITION)<EOL>self._prefix = settings.get("<STR_LIT>", '<STR_LIT:default>')<EOL>if not exists(self.host):<EOL><INDENT>os.makedirs(self.host, <NUM_LIT>)  <EOL><DEDENT>if not isdir(self.host):<EOL><INDENT>raise SessionConfigurationError('<STR_LIT>')<EOL><DEDENT>
Initialize File Session Driver.
settings section 'host' is recommended, the option 'prefix' is an optional.
if prefix is not given, 'default' is the default.
host: where to save session object file, this is a directory path.
prefix: session file name's prefix. session file like: prefix@session_id