code: def _GetPurgeMessage(most_recent_step, most_recent_wall_time, event_step,
                       event_wall_time, num_expired):
    
    return ('Detected out of order event.step likely caused by a TensorFlow '
            'restart. Purging {} expired tensor events from Tensorboard display '
            'between the previous step: {} (timestamp: {}) and current step: {} '
            '(timestamp: {}).'
           ).format(num_expired, most_recent_step, most_recent_wall_time,
                    event_step, event_wall_time)
docs: Return the string message associated with TensorBoard purges.