code: def __getitem__(self, idx):
      return self.x[idx, None], self.y[idx, None]
  
imports: from unittest import TestCase
  from bigdl.orca.automl.model.base_pytorch_model import PytorchModelBuilder
  from torch.utils.data import Dataset, DataLoader
  import pytest
  import numpy
  import torch
  import torch.nn
label_desc: Use image node_id 3 for calling the LinearDataset obj's underlying member method code with example usage: obj.__getitem__(idx) and returns: self,  self