Add `top_k` and `filter` fields to `ChatGPTPluginRetriever` (#2852)

This allows to adjust the number of results to retrieve and filter
documents based on metadata.

---------

Co-authored-by: Altay Sansal <altay.sansal@tgs.com>

langchain/retrievers/chatgpt_plugin_retriever.py

@@ -1,4 +1,6 @@
-from typing import List, Optional
+from __future__ import annotations
+
+from typing import List
 
 import aiohttp
 import requests
@@ -10,7 +12,9 @@ from langchain.schema import BaseRetriever, Document
 class ChatGPTPluginRetriever(BaseRetriever, BaseModel):
     url: str
     bearer_token: str
-    aiosession: Optional[aiohttp.ClientSession] = None
+    top_k: int = 3
+    filter: dict | None = None
+    aiosession: aiohttp.ClientSession | None = None
 
     class Config:
         """Configuration for this pydantic object."""
@@ -18,14 +22,8 @@ class ChatGPTPluginRetriever(BaseRetriever, BaseModel):
         arbitrary_types_allowed = True
 
     def get_relevant_documents(self, query: str) -> List[Document]:
-        response = requests.post(
-            f"{self.url}/query",
-            json={"queries": [{"query": query}]},
-            headers={
-                "Content-Type": "application/json",
-                "Authorization": f"Bearer {self.bearer_token}",
-            },
-        )
+        url, json, headers = self._create_request(query)
+        response = requests.post(url, json=json, headers=headers)
         results = response.json()["results"][0]["results"]
         docs = []
         for d in results:
@@ -34,12 +32,7 @@ class ChatGPTPluginRetriever(BaseRetriever, BaseModel):
         return docs
 
     async def aget_relevant_documents(self, query: str) -> List[Document]:
-        url = f"{self.url}/query"
-        json = {"queries": [{"query": query}]}
-        headers = {
-            "Content-Type": "application/json",
-            "Authorization": f"Bearer {self.bearer_token}",
-        }
+        url, json, headers = self._create_request(query)
 
         if not self.aiosession:
             async with aiohttp.ClientSession() as session:
@@ -57,3 +50,20 @@ class ChatGPTPluginRetriever(BaseRetriever, BaseModel):
             content = d.pop("text")
             docs.append(Document(page_content=content, metadata=d))
         return docs
+
+    def _create_request(self, query: str) -> tuple[str, dict, dict]:
+        url = f"{self.url}/query"
+        json = {
+            "queries": [
+                {
+                    "query": query,
+                    "filter": self.filter,
+                    "top_k": self.top_k,
+                }
+            ]
+        }
+        headers = {
+            "Content-Type": "application/json",
+            "Authorization": f"Bearer {self.bearer_token}",
+        }
+        return url, json, headers