So by saying “create a separate Data object for your training, testing and validation data sets.”
Do you mean that I could convert my current data construction:
    data = Data(x = x, 
                edge_index = edge_index,
                num_classes = 2,
    )

Into something like:
    train_mask = Data(x = x[0:300], 
                edge_index = edge_index,
                num_classes = 2,
    )
    test_mask = Data(x = x[300:], 
                edge_index = edge_index,
                num_classes = 2,
    )