Save the session for later retrieval

        :raises: IOError

def save(self):
        """Save the session for later retrieval

        :raises: IOError

        """
        try:
            with open(self._filename, 'wb') as session_file:
                session_file.write(self.dumps())
        except IOError as error:
            LOGGER.error('Session file error: %s', error)
            raise error