add websocket example

cookbook/pocketflow-fastapi-websocket/utils/__init__.py

@@ -0,0 +1 @@
+# Utils package for FastAPI WebSocket Chat Interface 

cookbook/pocketflow-fastapi-websocket/utils/stream_llm.py

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+import os
+from openai import OpenAI
+
+def stream_llm(messages):
+    client = OpenAI(api_key=os.environ.get("OPENAI_API_KEY", "your-api-key"))
+    
+    stream = client.chat.completions.create(
+        model="gpt-4o-mini",
+        messages=messages,
+        stream=True,
+        temperature=0.7
+    )
+    
+    for chunk in stream:
+        if chunk.choices[0].delta.content is not None:
+            yield chunk.choices[0].delta.content
+
+if __name__ == "__main__":
+    messages = [{"role": "user", "content": "Hello!"}]
+    for chunk in stream_llm(messages):
+        print(chunk, end="", flush=True)
+    print()