def delete_all_possible_task_files(self, courseid, taskid):
        """ Deletes all possibles task files in directory, to allow to change the format """
        if not id_checker(courseid):
            raise InvalidNameException("Course with invalid name: " + courseid)
        if not id_checker(taskid):
            raise InvalidNameException("Task with invalid name: " + taskid)
        task_fs = self.get_task_fs(courseid, taskid)
        for ext in self.get_available_task_file_extensions():
            try:
                task_fs.delete("task."+ext)
            except:
                pass
Deletes all possibles task files in directory, to allow to change the format