Generate and print out the log message for inference.

def log_inference(batch_id, batch_num, metric, step_loss, log_interval):
    """Generate and print out the log message for inference.
    """
    metric_nm, metric_val = metric.get()
    if not isinstance(metric_nm, list):
        metric_nm = [metric_nm]
        metric_val = [metric_val]

    eval_str = '[Batch %d/%d] loss=%.4f, metrics:' + \
               ','.join([i + ':%.4f' for i in metric_nm])
    logging.info(eval_str, batch_id + 1, batch_num, \
                 step_loss / log_interval, \
                 *metric_val)