Training my own data(6 classes) as cityscapes-format, but got eval [0. 0.00423967 0.35140248 0. 0. 0. ]

[shata-wh]

I made my own data as Cityscapes Dataset format, but my dataset only has 6 classes labeled 0-5.
I change the "self.label_mapping" in lib/datasets/cityscapes.py:
self.label_mapping = {0: 0, 1: 1, 2: 2, 3: 3, 4: 4, 5: 5}
But when I was training, the eval on val is:
[0. 0.00423967 0.35140248 0. 0. 0. ]

Could you tell me how to fix this problem? Was there anything I forgot to modify?