return invalid request with no json. Use union for older Python versi…

…ons. Update abstract method type annotations for Approach

app/backend/app.py

@@ -84,6 +84,8 @@ def content_file(path):
 @app.route("/ask", methods=["POST"])
 def ask():
     ensure_openai_token()
+    if not request.json:
+        return jsonify({"error": "request must be json"}), 400
     approach = request.json["approach"]
     try:
         impl = ask_approaches.get(approach)
@@ -98,6 +100,8 @@ def ask():
 @app.route("/chat", methods=["POST"])
 def chat():
     ensure_openai_token()
+    if not request.json:
+        return jsonify({"error": "request must be json"}), 400
     approach = request.json["approach"]
     try:
         impl = chat_approaches.get(approach)

app/backend/approaches/approach.py

@@ -2,5 +2,5 @@
 
 
 class Approach:
-    def run(self, q: str, use_summaries: bool) -> Any:
+    def run(self, q: str, overrides: dict[str, Any]) -> Any:
         raise NotImplementedError

app/backend/langchainadapters.py

@@ -1,8 +1,8 @@
-from typing import Any, Dict, List, Optional
+from typing import Any, Dict, List, Optional, Union
 from langchain.callbacks.base import BaseCallbackHandler
 from langchain.schema import AgentAction, AgentFinish, LLMResult
 
-def ch(text: str | object) -> str:
+def ch(text: Union[str, object]) -> str:
     s = text if isinstance(text, str) else str(text)
     return s.replace("<", "&lt;").replace(">", "&gt;").replace("\r", "").replace("\n", "<br>")
 

app/backend/lookuptool.py

@@ -2,12 +2,12 @@
 from pathlib import Path
 from langchain.agents import Tool
 from langchain.callbacks.manager import Callbacks
-from typing import Optional
+from typing import Optional, Union
 
 class CsvLookupTool(Tool):
     data: dict[str, str] = {}
 
-    def __init__(self, filename: str | Path, key_field: str, name: str = "lookup", 
+    def __init__(self, filename: Union[str, Path], key_field: str, name: str = "lookup", 
                  description: str = "useful to look up details given an input key as opposite to searching data with an unstructured question",
                  callbacks: Callbacks = None):
         super().__init__(name, self.lookup, description, callbacks=callbacks)