fix(reranker): reproduce ignoring top_n (#7025)

* fix(reranker): reproduce ignoring top_n

Signed-off-by: Mikhail Khludnev <mkhl@apache.org>

* fix(reranker): ignoring top_n

Signed-off-by: Mikhail Khludnev <mkhl@apache.org>

---------

Signed-off-by: Mikhail Khludnev <mkhl@apache.org>

Author: mkhludnev

backend/python/rerankers/backend.py

@@ -61,7 +61,7 @@ def LoadModel(self, request, context):
             if request.PipelineType != "": # Reuse the PipelineType field for language
                 kwargs['lang'] = request.PipelineType
             self.model_name = model_name
-            self.model = Reranker(model_name, **kwargs)  
+            self.model = Reranker(model_name, **kwargs)
         except Exception as err:
             return backend_pb2.Result(success=False, message=f"Unexpected {err=}, {type(err)=}")
 
@@ -80,7 +80,7 @@ def Rerank(self, request, context):
                 index=res.doc_id,
                 text=res.text,
                 relevance_score=res.score
-            ) for res in ranked_results.results
+            ) for res in ranked_results.top_k(request.top_n)
         ]
 
         # Calculate the usage and total tokens

backend/python/rerankers/test.py

@@ -86,5 +86,33 @@ def test_rerank(self):
         except Exception as err:
             print(err)
             self.fail("Reranker service failed")
+        finally:
+            self.tearDown()
+
+    def test_rerank_crop(self):
+        """
+        This method tests if the embeddings are generated successfully
+        """
+        try:
+            self.setUp()
+            with grpc.insecure_channel("localhost:50051") as channel:
+                stub = backend_pb2_grpc.BackendStub(channel)
+                request = backend_pb2.RerankRequest(
+                    query="I love you",
+                    documents=["I hate you", "I really like you", "I hate ignoring top_n"],
+                    top_n=2
+                )
+                response = stub.LoadModel(backend_pb2.ModelOptions(Model="cross-encoder"))
+                self.assertTrue(response.success)
+               
+                rerank_response = stub.Rerank(request)
+                print(rerank_response.results[0])
+                self.assertIsNotNone(rerank_response.results)
+                self.assertEqual(len(rerank_response.results), 2)
+                self.assertEqual(rerank_response.results[0].text, "I really like you")
+                self.assertEqual(rerank_response.results[1].text, "I hate you")
+        except Exception as err:
+            print(err)
+            self.fail("Reranker service failed")
         finally:
             self.tearDown()