code: def test_knn_graph():
      assert str(KNNGraph()) == "KNNGraph(k=6)"
  
      pos = torch.tensor(
          [
              [0.0, 0.0],
              [1.0, 0.0],
              [2.0, 0.0],
              [0.0, 1.0],
              [-2.0, 0.0],
              [0.0, -2.0],
          ]
      )
  
      expected_row = [
          0,
          0,
          0,
          0,
          0,
          1,
          1,
          1,
          1,
          2,
          2,
          3,
          3,
          3,
          4,
          4,
          5,
          5,
      ]
      expected_col = [
          1,
          2,
          3,
          4,
          5,
          0,
          2,
          3,
          5,
          0,
          1,
          0,
          1,
          4,
          0,
          3,
          0,
          1,
      ]
  
      data = Data(pos=pos)
      data = KNNGraph(k=2, force_undirected=True)(data)
      assert len(data) == 2
      assert data.pos.tolist() == pos.tolist()
      assert data.edge_index[0].tolist() == expected_row
      assert data.edge_index[1].tolist() == expected_col
  
imports: import torch
  from torch_geometric.data import Data
  from torch_geometric.testing import withPackage
  from torch_geometric.transforms import KNNGraph
label_desc: Use image node_id 1 for calling a global function with example usage: test_knn_graph() without return types