[GraphBolt] Add names to `ItemSets` in `_init_all_nodes_set` (#6461)

python/dgl/graphbolt/impl/ondisk_dataset.py

@@ -11,6 +11,7 @@ import yaml
 
 import dgl
 
+from ...base import dgl_warning
 from ...data.utils import download, extract_archive
 from ..base import etype_str_to_tuple
 from ..dataset import Dataset, Task
@@ -498,13 +499,16 @@ class OnDiskDataset(Dataset):
 
     def _init_all_nodes_set(self, graph) -> Union[ItemSet, ItemSetDict]:
         if graph is None:
+            dgl_warning(
+                "`all_node_set` is returned as None, since graph is None."
+            )
             return None
         num_nodes = graph.num_nodes
         if isinstance(num_nodes, int):
-            return ItemSet(num_nodes)
+            return ItemSet(num_nodes, names="seed_nodes")
         else:
             data = {
-                node_type: ItemSet(num_node)
+                node_type: ItemSet(num_node, names="seed_nodes")
                 for node_type, num_node in num_nodes.items()
             }
             return ItemSetDict(data)

tests/python/pytorch/graphbolt/impl/test_ondisk_dataset.py

@@ -1806,6 +1806,7 @@ def test_OnDiskDataset_all_nodes_set_homo():
         dataset = gb.OnDiskDataset(test_dir).load()
         all_nodes_set = dataset.all_nodes_set
         assert isinstance(all_nodes_set, gb.ItemSet)
+        assert all_nodes_set.names == ("seed_nodes",)
         for i, item in enumerate(all_nodes_set):
             assert i == item
 
@@ -1842,6 +1843,7 @@ def test_OnDiskDataset_all_nodes_set_hetero():
         dataset = gb.OnDiskDataset(test_dir).load()
         all_nodes_set = dataset.all_nodes_set
         assert isinstance(all_nodes_set, gb.ItemSetDict)
+        assert all_nodes_set.names == ("seed_nodes",)
         for i, item in enumerate(all_nodes_set):
             assert len(item) == 1
             assert isinstance(item, dict)