>>> cache = Cache(log_level=logging.WARNING)
        >>> cache.shutdown_thread_pool()
        True
        >>> cache.unable_thread_pool()
        True
        >>> cache.shutdown_thread_pool()
        False

def shutdown_thread_pool(self, only_read=False):
        """
        >>> cache = Cache(log_level=logging.WARNING)
        >>> cache.shutdown_thread_pool()
        True
        >>> cache.unable_thread_pool()
        True
        >>> cache.shutdown_thread_pool()
        False
        """
        if self.enable_thread_pool and hasattr(self, 'thread_pool') and self.thread_pool is not None:
            self.thread_pool.shutdown()
            return True
        else:
            self.logger.warning('Current not have a thread pool is existent')
            return False