@eqy, if you mean by doing the evaluation process, I am getting the exact same error when running it
# Defining Labels and Predictions
truelabels = []
predictions = []
model.eval()
print("Getting predictions from test set...")
for data, target in test_loader:
    for label in target.data.numpy():
        truelabels.append(label)
    for prediction in model(data).data.numpy().argmax(1):
        predictions.append(prediction) 

# Plot the confusion matrix
cm = confusion_matrix(truelabels, predictions)
tick_marks = np.arange(len(classes))

df_cm = pd.DataFrame(cm, index = classes, columns = classes)
plt.figure(figsize = (7,7))
sns.heatmap(df_cm, annot=True, cmap=plt.cm.Blues, fmt='g')
plt.xlabel("Predicted Shape", fontsize = 20)
plt.ylabel("True Shape", fontsize = 20)
plt.show()

Getting predictions from test set...
---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-140-460554552293> in <module>
      7     for label in target.data.numpy():
      8         truelabels.append(label)
----> 9     for prediction in model(data).data.numpy().argmax([1]):
     10         predictions.append(prediction)
     11 

AttributeError: 'tuple' object has no attribute 'data'