def METHOD_NAME(self, scheduler_type):
    """
    :param scheduler_type: type of new scheduler: 'thread' or 'asyncio'
    :return: instance of scheduler
    """
    if self._scheduler_type == scheduler_type:
        return self._scheduler
    if scheduler_type == 'thread':
        scheduler = MolerThreadScheduler()
    elif scheduler_type == 'asyncio':
        scheduler = MolerAsyncioScheduler()
    else:
        raise WrongUsage(
            "Wrong value of 'scheduler_type': '{}'. Allowed are 'thread' or 'asyncio'".format(scheduler_type))
    scheduler.start()
    return scheduler