After I trained on my own 3D data and predicted on the test set, I found some samples with null predictions

[maolimin]

        "metrics": {
            "1": {
                "Dice": 0.0,
                "FN": 353,
                "FP": 0,
                "IoU": 0.0,
                "TN": 22478495,
                "TP": 0,
                "n_pred": 0,
                "n_ref": 353
            }
        },
        "prediction_file": "/data0/maolimin/U-Mamba/data/nnUNet_results/Dataset202_Breast/nnUNetTrainerUMambaBot__nnUNetPlans__3d_fullres/fold_0/validation/br_130.nii.gz",
        "reference_file": "/data0/maolimin/U-Mamba/data/nnUNet_preprocessed/Dataset202_Breast/gt_segmentations/br_130.nii.gz"

There are also cases where the inference is null on the validation set,Looking forward to your reply