Put a task into the queue.

        Args:
            value (str): Task data.
            priority (int): An optional priority as an integer with at most 3 digits.
                Lower values signify higher priority.

def put(self, value, priority=100):
        """
        Put a task into the queue.

        Args:
            value (str): Task data.
            priority (int): An optional priority as an integer with at most 3 digits.
                Lower values signify higher priority.
        """
        task_name = '{}{:03d}_{}'.format(self.TASK_PREFIX, priority, self._counter)
        path = posixpath.join(self._queue_path, task_name)
        self._client.kv[path] = value