Confusion matrix

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Does anyone know how to add the confusion matrix in this code? After I added it according to the online one, something went wrong. I don't know what went wrong in my code.I can't solve it. please help help me! Thanks.
def confusion_matrix(output, labels, conf_matrix):

preds = torch.argmax(output, dim=-1)
for p, t in zip(preds, labels):
    conf_matrix[p, t] += 1
return conf_matrix