[Misc] Auto fix by black. (#4952)

* black on explain_main

* isort

* add dot
Co-authored-by: Steve <ubuntu@ip-172-31-34-29.ap-northeast-1.compute.internal>

examples/pytorch/gnn_explainer/explain_main.py

 import argparse
 import os
-import dgl
-from gnnlens import Writer
+
 import torch as th
+from gnnlens import Writer
+from models import Model
 
+import dgl
 from dgl import load_graphs
+from dgl.data import (BACommunityDataset, BAShapeDataset, TreeCycleDataset,
+                      TreeGridDataset)
 from dgl.nn import GNNExplainer
-from models import Model
 
-from dgl.data import BAShapeDataset, BACommunityDataset, TreeCycleDataset, TreeGridDataset
 
 def main(args):
-    if args.dataset == 'BAShape':
+    if args.dataset == "BAShape":
         dataset = BAShapeDataset(seed=0)
-    elif args.dataset == 'BACommunity':
+    elif args.dataset == "BACommunity":
         dataset = BACommunityDataset(seed=0)
-    elif args.dataset == 'TreeCycle':
+    elif args.dataset == "TreeCycle":
         dataset = TreeCycleDataset(seed=0)
-    elif args.dataset == 'TreeGrid':
+    elif args.dataset == "TreeGrid":
         dataset = TreeGridDataset(seed=0)
 
     graph = dataset[0]
-    labels = graph.ndata['label']
-    feats = graph.ndata['feat']
+    labels = graph.ndata["label"]
+    feats = graph.ndata["feat"]
     num_classes = dataset.num_classes
 
     # load an existing model
-    model_path = os.path.join('./', f'model_{args.dataset}.pth')
+    model_path = os.path.join("./", f"model_{args.dataset}.pth")
     model_stat_dict = th.load(model_path)
     model = Model(feats.shape[-1], num_classes)
     model.load_state_dict(model_stat_dict)
@@ -38,29 +40,41 @@ def main(args):
             break
 
     explainer = GNNExplainer(model, num_hops=3)
-    new_center, sub_graph, feat_mask, edge_mask = explainer.explain_node(n_idx, graph, feats)
+    new_center, sub_graph, feat_mask, edge_mask = explainer.explain_node(
+        n_idx, graph, feats
+    )
 
     # gnnlens2
     # Specify the path to create a new directory for dumping data files.
-    writer = Writer('gnn_subgraph')
-    writer.add_graph(name=args.dataset, graph=graph,
-                     nlabels=labels, num_nlabel_types=num_classes)
-    writer.add_subgraph(graph_name=args.dataset,
-                        subgraph_name='GNNExplainer',
-                        node_id=n_idx,
-                        subgraph_nids=sub_graph.ndata[dgl.NID],
-                        subgraph_eids=sub_graph.edata[dgl.EID],
-                        subgraph_eweights=edge_mask)
+    writer = Writer("gnn_subgraph")
+    writer.add_graph(
+        name=args.dataset,
+        graph=graph,
+        nlabels=labels,
+        num_nlabel_types=num_classes,
+    )
+    writer.add_subgraph(
+        graph_name=args.dataset,
+        subgraph_name="GNNExplainer",
+        node_id=n_idx,
+        subgraph_nids=sub_graph.ndata[dgl.NID],
+        subgraph_eids=sub_graph.edata[dgl.EID],
+        subgraph_eweights=edge_mask,
+    )
 
-    # Finish dumping
+    # Finish dumping.
     writer.close()
 
-if __name__ == '__main__':
-    parser = argparse.ArgumentParser(description='Demo of GNN explainer in DGL')
-    parser.add_argument('--dataset', type=str, default='BAShape',
-                        choices=['BAShape', 'BACommunity', 'TreeCycle', 'TreeGrid'])
+
+if __name__ == "__main__":
+    parser = argparse.ArgumentParser(description="Demo of GNN explainer in DGL")
+    parser.add_argument(
+        "--dataset",
+        type=str,
+        default="BAShape",
+        choices=["BAShape", "BACommunity", "TreeCycle", "TreeGrid"],
+    )
     args = parser.parse_args()
     print(args)
 
     main(args)
-