Update docstring about cross validation fold usage

Signed-off-by: MaybeRichard <[email protected]>

generation/maisi/maisi_train_controlnet_tutorial.ipynb

@@ -166,7 +166,7 @@
     "            \"image\": \"tr_image_001_emb.nii.gz\",  # relative path to the image embedding file\n",
     "            # relative path to the combined label (pseudo whole-body segmentation mask + ROI mask) file\n",
     "            \"label\": \"tr_label_001.nii.gz\",\n",
-    "            \"fold\": 0,  # fold index for cross validation, fold 0 is used for training\n",
+    "            \"fold\": 0,  # fold index for cross validation. If the dataset item's fold value is equal to the fold value in config_maisi_controlnet_train.json, then it is used for validation. Otherwise, it is used for training. In the current parameters, fold 0 is for validation and fold 1 is for training.\n",
     "            \"dim\": sim_dim,  # the dimension of image\n",
     "            \"spacing\": [1.5, 1.5, 1.5],  # the spacing of image\n",
     "            \"top_region_index\": [0, 1, 0, 0],  # the top region index of the image\n",