[Temporal]Fix tensor option mismatch issue (#7346)

Co-authored-by: Ubuntu <ubuntu@ip-172-31-21-218.ap-northeast-1.compute.internal>

graphbolt/src/fused_csc_sampling_graph.cc

@@ -873,11 +873,16 @@ std::pair<bool, std::vector<int64_t>> FastTemporalPick(
       continue;
     }
     if (node_timestamp.has_value()) {
+      bool flag = true;
+      AT_DISPATCH_INDEX_TYPES(
+          csc_indices.scalar_type(), "CheckNodeTimeStamp", ([&] {
             int64_t neighbor_id =
-          utils::GetValueByIndex<int64_t>(csc_indices, edge_id);
+                utils::GetValueByIndex<index_t>(csc_indices, edge_id);
             if (utils::GetValueByIndex<int64_t>(
                     node_timestamp.value(), neighbor_id) >= timestamp)
-        continue;
+              flag = false;
+          }));
+      if (!flag) continue;
     }
     if (edge_timestamp.has_value() &&
         utils::GetValueByIndex<int64_t>(edge_timestamp.value(), edge_id) >=

python/dgl/graphbolt/impl/temporal_neighbor_sampler.py

@@ -95,11 +95,18 @@ class TemporalNeighborSampler(SubgraphSampler):
         ), "seeds_timestamp must be provided for temporal neighbor sampling."
         subgraphs = []
         num_layers = len(self.fanouts)
-        # Enrich seeds with all node types.
+        # Enrich seeds with all node types. Ensure that the dtype and device
+        # remain consistent with those of the existing seeds.
         if isinstance(seeds, dict):
+            first_val = next(iter(seeds.items()))[1]
             ntypes = list(self.graph.node_type_to_id.keys())
             seeds = {
-                ntype: seeds.get(ntype, torch.LongTensor([]))
+                ntype: seeds.get(
+                    ntype,
+                    torch.tensor(
+                        [], dtype=first_val.dtype, device=first_val.device
+                    ),
+                )
                 for ntype in ntypes
             }
             seeds_timestamp = {