add dashscope reranker support

src/pymilvus/model/reranker/__init__.py

@@ -4,6 +4,7 @@
 from pymilvus.model.reranker.cross_encoder import CrossEncoderRerankFunction
 from pymilvus.model.reranker.jinaai import JinaRerankFunction
 from pymilvus.model.reranker.tei import TEIRerankFunction
+from pymilvus.model.reranker.dashscope import DashscopeRerankFunction
 
 __all__ = [
     "CohereRerankFunction",
@@ -12,4 +13,5 @@
     "CrossEncoderRerankFunction",
     "JinaRerankFunction",
     "TEIRerankFunction",
+    "DashscopeRerankFunction",
 ]

src/pymilvus/model/reranker/dashscope.py

@@ -0,0 +1,62 @@
+import os
+from typing import List, Optional
+
+import requests
+
+from pymilvus.model.base import BaseRerankFunction, RerankResult
+
+API_URL = "https://dashscope.aliyuncs.com/api/v1/services/rerank/text-rerank/text-rerank"
+
+
+class DashscopeRerankFunction(BaseRerankFunction):
+    def __init__(self, model_name: str = "qwen3-rerank", api_key: Optional[str] = None,  **kwargs):
+        if api_key is None:
+            if "DASHSCOPE_API_KEY" in os.environ and os.environ["DASHSCOPE_API_KEY"]:
+                self.api_key = os.environ["DASHSCOPE_API_KEY"]
+            else:
+                error_message = (
+                    "Did not find api_key, please add an environment variable"
+                    " `DASHSCOPE_API_KEY` which contains it, or pass"
+                    "  `api_key` as a named parameter."
+                )
+                raise ValueError(error_message)
+        else:
+            self.api_key = api_key
+        self.model_name = model_name
+        self._session = requests.Session()
+        self._session.headers.update(
+            {"Authorization": f"Bearer {self.api_key}", "Accept-Encoding": "identity"}
+        )
+        self.model_name = model_name
+        self.rerank_config = {**kwargs} 
+
+    def __call__(self, query: str, documents: List[str], top_k: int = 5) -> List[RerankResult]:
+        json_data = {
+            "model": self.model_name,
+            "input":{
+                "query": query,
+                "documents": documents,
+            },
+        }
+        if self.rerank_config:
+            json_data["parameters"] = self.rerank_config
+        else:
+            json_data["parameters"] = {}
+        json_data["parameters"]["top_n"] = top_k
+        resp = self._session.post(  # type: ignore[assignment]
+            API_URL,
+            json=json_data,
+        ).json()
+        if "output" not in resp:
+            raise RuntimeError(resp["output"])
+
+        results = []
+        for res in resp["output"]["results"]:
+            results.append(
+                RerankResult(
+                    text=res.get("document", {}).get("text", ""), 
+                    score=res["relevance_score"], 
+                    index=res["index"]
+                )
+            )
+        return results