📝 Fix typing issue in `docs_src/app_testing/app_b` code example (#14573)

Co-authored-by: pre-commit-ci-lite[bot] <117423508+pre-commit-ci-lite[bot]@users.noreply.github.com>
Co-authored-by: Motov Yurii <[email protected]>

docs_src/app_testing/app_b_an_py310/main.py

@@ -34,5 +34,5 @@ async def create_item(item: Item, x_token: Annotated[str, Header()]) -> Item:
         raise HTTPException(status_code=400, detail="Invalid X-Token header")
     if item.id in fake_db:
         raise HTTPException(status_code=409, detail="Item already exists")
-    fake_db[item.id] = item
+    fake_db[item.id] = item.model_dump()
     return item

docs_src/app_testing/app_b_an_py39/main.py

@@ -34,5 +34,5 @@ async def create_item(item: Item, x_token: Annotated[str, Header()]) -> Item:
         raise HTTPException(status_code=400, detail="Invalid X-Token header")
     if item.id in fake_db:
         raise HTTPException(status_code=409, detail="Item already exists")
-    fake_db[item.id] = item
+    fake_db[item.id] = item.model_dump()
     return item

docs_src/app_testing/app_b_py310/main.py

@@ -32,5 +32,5 @@ async def create_item(item: Item, x_token: str = Header()) -> Item:
         raise HTTPException(status_code=400, detail="Invalid X-Token header")
     if item.id in fake_db:
         raise HTTPException(status_code=409, detail="Item already exists")
-    fake_db[item.id] = item
+    fake_db[item.id] = item.model_dump()
     return item

docs_src/app_testing/app_b_py39/main.py

@@ -34,5 +34,5 @@ async def create_item(item: Item, x_token: str = Header()) -> Item:
         raise HTTPException(status_code=400, detail="Invalid X-Token header")
     if item.id in fake_db:
         raise HTTPException(status_code=409, detail="Item already exists")
-    fake_db[item.id] = item
+    fake_db[item.id] = item.model_dump()
     return item