Mismatch in Mask Dimensions for Multi-Class Segmentation (3 Classes)

The default class_nums = 1, but if i want to change it to 3, and the mask I provided have 3 classes, the data preprocessing for the mask(y_pred) only have 1 dim not 3 dims, but the model 's output(y) has 3 dims, so an error occured ! Please tell me how to solve this problem. Thanks!

Start by locating the class_nums configuration and tracing the mask preprocessing alongside the model output for a three-class example. Reproduce the reported dimension mismatch with the provided three-class mask. Done means preprocessing produces dimensions compatible with the model output and the error no longer occurs.

Written by the indexing model from the issue text.