cohere[patch]: Fix cohere rerank (langchain-ai#19624)

Fix cohere rerank inspired by
langchain-ai#19486

libs/partners/cohere/langchain_cohere/rerank.py

@@ -69,10 +69,14 @@ def rerank(
         model = model or self.model
         top_n = top_n if (top_n is None or top_n > 0) else self.top_n
         results = self.client.rerank(
-            query, docs, model, top_n=top_n, max_chunks_per_doc=max_chunks_per_doc
+            query=query,
+            documents=docs,
+            model=model,
+            top_n=top_n,
+            max_chunks_per_doc=max_chunks_per_doc,
         )
         result_dicts = []
-        for res in results:
+        for res in results.results:
             result_dicts.append(
                 {"index": res.index, "relevance_score": res.relevance_score}
             )

libs/partners/cohere/tests/integration_tests/test_rerank.py

@@ -0,0 +1,16 @@
+"""Test Cohere reranks."""
+from langchain_core.documents import Document
+
+from langchain_cohere import CohereRerank
+
+
+def test_langchain_cohere_rerank_documents() -> None:
+    """Test cohere rerank."""
+    rerank = CohereRerank()
+    test_documents = [
+        Document(page_content="This is a test document."),
+        Document(page_content="Another test document."),
+    ]
+    test_query = "Test query"
+    results = rerank.rerank(test_documents, test_query)
+    assert len(results) == 2