Add import_or_fail decorator to lagranginan tests (#707)

* Update test_lagrangian.py

Author: ktangsali

test/datapipes/test_lagrangian.py

@@ -60,8 +60,9 @@ def test_lagrangian_dataset_constructor(data_dir, device, pytestconfig):
     assert graph.ndata["y"].shape[-1] > 0  # node targets
 
 
+@import_or_fail(["tensorflow", "dgl"])
 @pytest.mark.parametrize("device", ["cuda:0", "cpu"])
-def test_graph_construction(device):
+def test_graph_construction(device, pytestconfig):
     from modulus.datapipes.gnn.lagrangian_dataset import compute_edge_index
 
     mesh_pos = torch.tensor([[0.0, 0.0], [0.01, 0.0], [1.0, 1.0]], device=device)