code: def test_constant():
      assert str(Constant()) == "Constant(value=1.0)"
  
      x = torch.tensor([[-1, 0], [0, 0], [2, 0]], dtype=torch.float)
      edge_index = torch.tensor([[0, 1], [1, 2]])
  
      data = Data(edge_index=edge_index, num_nodes=3)
      data = Constant()(data)
      assert len(data) == 3
      assert data.edge_index.tolist() == edge_index.tolist()
      assert data.x.tolist() == [[1], [1], [1]]
      assert data.num_nodes == 3
  
      data = Data(edge_index=edge_index, x=x)
      data = Constant()(data)
      assert len(data) == 2
      assert data.edge_index.tolist() == edge_index.tolist()
      assert data.x.tolist() == [[-1, 0, 1], [0, 0, 1], [2, 0, 1]]
  
      data = HeteroData()
      data["v"].x = x
      data = Constant()(data)
      assert len(data) == 1
      assert data["v"].x.tolist() == [[-1, 0, 1], [0, 0, 1], [2, 0, 1]]
  
      data = HeteroData()
      data["v"].x = x
      data["w"].x = x
      data = Constant(node_types="w")(data)
      assert len(data) == 1
      assert data["v"].x.tolist() == x.tolist()
      assert data["w"].x.tolist() == [[-1, 0, 1], [0, 0, 1], [2, 0, 1]]
  
label_desc: Use image node_id 1 for calling a global function with example usage: test_constant() without return types