code: def test_mlp_aggregation():
      x = torch.randn(6, 16)
      index = torch.tensor([0, 0, 1, 1, 1, 2])
  
      aggr = MLPAggregation(
          in_channels=16,
          out_channels=32,
          max_num_elements=3,
          num_layers=1,
      )
      assert str(aggr) == "MLPAggregation(16, 32, max_num_elements=3)"
  
      out = aggr(x, index)
      assert out.size() == (3, 32)
  
label_desc: Use image node_id 1 for calling a global function with example usage: test_mlp_aggregation() without return types