更换训练数据后，类别数更改就报错，原来18类别现在2类别

[berrybobo]

RuntimeError: Error(s) in loading state_dict for RobertaForSequenceClassification: size mismatch for classifier.out_proj.weight: copying a param with shape torch.Size([18, 768]) from checkpoint, the shape in current model is torch.Size([2, 768]). size mismatch for classifier.out_proj.bias: copying a param with shape torch.Size([18]) from checkpoint, the shape in current model is torch.Size([2]). You may consider adding ignore_mismatched_sizes=True in the model from_pretrained method.