FastAPI - Error Handling
Given this FastAPI code snippet, what will be the JSON response body when a 400 error occurs?
```python
from fastapi import FastAPI, HTTPException
from pydantic import BaseModel
class ErrorResponse(BaseModel):
detail: str
app = FastAPI()
@app.get("/items/{item_id}", responses={400: {"model": ErrorResponse}})
async def read_item(item_id: int):
if item_id < 0:
raise HTTPException(status_code=400, detail="Invalid item ID")
return {"item_id": item_id}
```