Ploting ROC curve for multiclass classification

I am trying to plot ROC curve for multi class classification.I would like to plot multiple lines in a single graph for each class.But I am getting error
Error Traceback (most recent call last): File "/home/ex/Downloads/HW/", line 385, in <module> plot_roc(actuals, class_probabilities,n_class) File "/home/ex/Downloads/HW/", line 230, in plot_roc fpr[i], tpr[i], _ = roc_curve(actuals[:, i], probabilities[:, i]) TypeError: list indices must be integers or slices, not tuple
I could not understand how I will get rid of this error.
Here is my code that I used

def test_class_probabilities(model, test_loader, n_class):
    actuals = []
    probabilities = []
    with torch.no_grad():
        for sample in test_loader:
            labels = Variable(sample['grade'])
            inputs = Variable(sample['image'])

            outputs = net(inputs).squeeze()

            prediction = outputs.argmax(dim=1, keepdim=True)
            actuals.extend(labels.view_as(prediction) == n_class)
            probabilities.extend(np.exp(outputs[:, n_class]))
    return actuals,probabilities                     #[i.item() for i in actuals], [i.item() for i in probabilities]

def plot_roc( actuals,  probabilities, n_classes):
    compute ROC curve and ROC area for each class in each fold


    fpr = dict()
    tpr = dict()
    roc_auc = dict()
    for i in range(n_classes):
        fpr[i], tpr[i], _ = roc_curve(actuals[:, i], probabilities[:, i])
        roc_auc[i] = auc(fpr[i], tpr[i])

    # plt.figure(figsize=(6,6))
    for i in range(n_classes):
        plt.plot(fpr[i], tpr[i], label='ROC curve of class {0} (area = {1:0.2f})'
                                       ''.format(i, roc_auc[i]))  # roc_auc_score

    plt.plot([0, 1], [0, 1], 'k--')
    # plt.grid()
    plt.xlim([0.0, 1.0])
    plt.ylim([0.0, 1.05])
    plt.xlabel('False Positive Rate')
    plt.ylabel('True Positive Rate')
    plt.title('Receiver operating characteristic to multi-class')
    plt.legend(loc="lower right")
    # plt.tight_layout()

actuals is a list, but you’re trying to index into it with two values (:, i). Python lists are not arrays and can’t be indexed into with a comma-separated list of indices.

Replace actuals[:, i] with actuals[i] and probabilities[:, i] with probabilities[i].