code: def test_cartesian():
      assert str(Cartesian()) == "Cartesian(norm=True, max_value=None)"
  
      pos = torch.tensor([[-1.0, 0.0], [0.0, 0.0], [2.0, 0.0]])
      edge_index = torch.tensor([[0, 1, 1, 2], [1, 0, 2, 1]])
      edge_attr = torch.tensor([1.0, 2.0, 3.0, 4.0])
  
      data = Data(edge_index=edge_index, pos=pos)
      data = Cartesian(norm=False)(data)
      assert len(data) == 3
      assert torch.equal(data.pos, pos)
      assert torch.equal(data.edge_index, edge_index)
      assert torch.allclose(
          data.edge_attr,
          torch.tensor(
              [[-1.0, 0.0], [1.0, 0.0], [-2.0, 0.0], [2.0, 0.0]]
          ),
      )
  
      data = Data(edge_index=edge_index, pos=pos, edge_attr=edge_attr)
      data = Cartesian(norm=True)(data)
      assert len(data) == 3
      assert torch.equal(data.pos, pos)
      assert torch.equal(data.edge_index, edge_index)
      assert torch.allclose(
          data.edge_attr,
          torch.tensor(
              [
                  [1, 0.25, 0.5],
                  [2, 0.75, 0.5],
                  [3, 0, 0.5],
                  [4, 1, 0.5],
              ]
          ),
      )
  
label_desc: Use image node_id 1 for calling a global function with example usage: test_cartesian() without return types