Sync fastapi docs from 50fa3f7c on 2026-01-11

docs_src/response_model/tutorial002_py39.py

@@ -0,0 +1,19 @@
+from typing import Union
+
+from fastapi import FastAPI
+from pydantic import BaseModel, EmailStr
+
+app = FastAPI()
+
+
+class UserIn(BaseModel):
+    username: str
+    password: str
+    email: EmailStr
+    full_name: Union[str, None] = None
+
+
+# Don't do this in production!
+@app.post("/user/")
+async def create_user(user: UserIn) -> UserIn:
+    return user