[GraphBolt] Add parameter to `NeighborSampler` to support NOT deduplication. (#6419)

Co-authored-by: Ubuntu <ubuntu@ip-172-31-0-133.us-west-2.compute.internal>

python/dgl/graphbolt/impl/neighbor_sampler.py

@@ -44,6 +44,10 @@ class NeighborSampler(SubgraphSampler):
         probabilities corresponding to each neighboring edge of a node.
         It must be a 1D floating-point or boolean tensor, with the number
         of elements equalling the total number of edges.
+    deduplicate: bool
+        Boolean indicating whether seeds between hops will be deduplicated.
+        If True, the same elements in seeds will be deleted to only one.
+        Otherwise, the same elements will be remained.
 
     Examples
     -------
@@ -77,6 +81,7 @@ class NeighborSampler(SubgraphSampler):
         fanouts,
         replace=False,
         prob_name=None,
+        deduplicate=True,
     ):
         super().__init__(datapipe)
         self.graph = graph
@@ -88,6 +93,7 @@ class NeighborSampler(SubgraphSampler):
             self.fanouts.append(fanout)
         self.replace = replace
         self.prob_name = prob_name
+        self.deduplicate = deduplicate
         self.sampler = graph.sample_neighbors
 
     def _sample_subgraphs(self, seeds):
@@ -108,9 +114,12 @@ class NeighborSampler(SubgraphSampler):
                 self.prob_name,
             )
             original_column_node_ids = seeds
-            seeds, compacted_node_pairs = unique_and_compact_node_pairs(
-                subgraph.node_pairs, seeds
-            )
+            if self.deduplicate:
+                seeds, compacted_node_pairs = unique_and_compact_node_pairs(
+                    subgraph.node_pairs, seeds
+                )
+            else:
+                raise RuntimeError("Not implemented yet.")
             subgraph = SampledSubgraphImpl(
                 node_pairs=compacted_node_pairs,
                 original_column_node_ids=original_column_node_ids,
@@ -166,6 +175,10 @@ class LayerNeighborSampler(NeighborSampler):
         probabilities corresponding to each neighboring edge of a node.
         It must be a 1D floating-point or boolean tensor, with the number
         of elements equalling the total number of edges.
+    deduplicate: bool
+            Boolean indicating whether seeds between hops will be deduplicated.
+            If True, the same elements in seeds will be deleted to only one.
+            Otherwise, the same elements will be remained.
 
     Examples
     -------
@@ -202,6 +215,9 @@ class LayerNeighborSampler(NeighborSampler):
         fanouts,
         replace=False,
         prob_name=None,
+        deduplicate=True,
     ):
-        super().__init__(datapipe, graph, fanouts, replace, prob_name)
+        super().__init__(
+            datapipe, graph, fanouts, replace, prob_name, deduplicate
+        )
         self.sampler = graph.sample_layer_neighbors