def set_modification_time(self, modification_time=True):
        """
        Add time to be written as last modification time

        When called after initialisation configure to use
        time of writing file
        """
        if (isinstance(modification_time, basestring) and
                modification_time.lower() == 'write') or\
                modification_time is True:
            self.modification_time = True
        else:
            self.modification_time = check_time(modification_time)