[GraphBolt] Refactor `NeighborSamplerImpl` (#7207)

python/dgl/graphbolt/impl/neighbor_sampler.py

@@ -230,8 +230,72 @@ class FetcherAndSampler(MiniBatchTransformer):
         super().__init__(datapipe)
 
 
+class NeighborSamplerImpl(SubgraphSampler):
+    # pylint: disable=abstract-method
+    """Base class for NeighborSamplers."""
+
+    # pylint: disable=useless-super-delegation
+    def __init__(
+        self,
+        datapipe,
+        graph,
+        fanouts,
+        replace,
+        prob_name,
+        deduplicate,
+        sampler,
+    ):
+        super().__init__(
+            datapipe, graph, fanouts, replace, prob_name, deduplicate, sampler
+        )
+
+    @staticmethod
+    def _prepare(node_type_to_id, minibatch):
+        seeds = minibatch._seed_nodes
+        # Enrich seeds with all node types.
+        if isinstance(seeds, dict):
+            ntypes = list(node_type_to_id.keys())
+            # Loop over different seeds to extract the device they are on.
+            device = None
+            dtype = None
+            for _, seed in seeds.items():
+                device = seed.device
+                dtype = seed.dtype
+                break
+            default_tensor = torch.tensor([], dtype=dtype, device=device)
+            seeds = {
+                ntype: seeds.get(ntype, default_tensor) for ntype in ntypes
+            }
+        minibatch._seed_nodes = seeds
+        minibatch.sampled_subgraphs = []
+        return minibatch
+
+    @staticmethod
+    def _set_input_nodes(minibatch):
+        minibatch.input_nodes = minibatch._seed_nodes
+        return minibatch
+
+    # pylint: disable=arguments-differ
+    def sampling_stages(
+        self, datapipe, graph, fanouts, replace, prob_name, deduplicate, sampler
+    ):
+        datapipe = datapipe.transform(
+            partial(self._prepare, graph.node_type_to_id)
+        )
+        for fanout in reversed(fanouts):
+            # Convert fanout to tensor.
+            if not isinstance(fanout, torch.Tensor):
+                fanout = torch.LongTensor([int(fanout)])
+            datapipe = datapipe.sample_per_layer(
+                sampler, fanout, replace, prob_name
+            )
+            datapipe = datapipe.compact_per_layer(deduplicate)
+
+        return datapipe.transform(self._set_input_nodes)
+
+
 @functional_datapipe("sample_neighbor")
-class NeighborSampler(SubgraphSampler):
+class NeighborSampler(NeighborSamplerImpl):
     # pylint: disable=abstract-method
     """Sample neighbor edges from a graph and return a subgraph.
 
@@ -323,61 +387,20 @@ class NeighborSampler(SubgraphSampler):
         replace=False,
         prob_name=None,
         deduplicate=True,
-        sampler=None,
     ):
-        if sampler is None:
-            sampler = graph.sample_neighbors
         super().__init__(
-            datapipe, graph, fanouts, replace, prob_name, deduplicate, sampler
-        )
-
-    @staticmethod
-    def _prepare(node_type_to_id, minibatch):
-        seeds = minibatch._seed_nodes
-        # Enrich seeds with all node types.
-        if isinstance(seeds, dict):
-            ntypes = list(node_type_to_id.keys())
-            # Loop over different seeds to extract the device they are on.
-            device = None
-            dtype = None
-            for _, seed in seeds.items():
-                device = seed.device
-                dtype = seed.dtype
-                break
-            default_tensor = torch.tensor([], dtype=dtype, device=device)
-            seeds = {
-                ntype: seeds.get(ntype, default_tensor) for ntype in ntypes
-            }
-        minibatch._seed_nodes = seeds
-        minibatch.sampled_subgraphs = []
-        return minibatch
-
-    @staticmethod
-    def _set_input_nodes(minibatch):
-        minibatch.input_nodes = minibatch._seed_nodes
-        return minibatch
-
-    # pylint: disable=arguments-differ
-    def sampling_stages(
-        self, datapipe, graph, fanouts, replace, prob_name, deduplicate, sampler
-    ):
-        datapipe = datapipe.transform(
-            partial(self._prepare, graph.node_type_to_id)
+            datapipe,
+            graph,
+            fanouts,
+            replace,
+            prob_name,
+            deduplicate,
+            graph.sample_neighbors,
         )
-        for fanout in reversed(fanouts):
-            # Convert fanout to tensor.
-            if not isinstance(fanout, torch.Tensor):
-                fanout = torch.LongTensor([int(fanout)])
-            datapipe = datapipe.sample_per_layer(
-                sampler, fanout, replace, prob_name
-            )
-            datapipe = datapipe.compact_per_layer(deduplicate)
-
-        return datapipe.transform(self._set_input_nodes)
 
 
 @functional_datapipe("sample_layer_neighbor")
-class LayerNeighborSampler(NeighborSampler):
+class LayerNeighborSampler(NeighborSamplerImpl):
     # pylint: disable=abstract-method
     """Sample layer neighbor edges from a graph and return a subgraph.