```python
from fastapi import FastAPI, Query
import asyncio
import helpers

app = FastAPI()


@app.get("/portfolio")
async def portfolio(symbols: str = Query(...)):
    sym_list = [s.strip() for s in symbols.split(",") if s.strip()]
    tasks = [helpers.afetch_price(s) for s in sym_list]
    prices_list = await asyncio.gather(*tasks)
    prices = {sym: price for sym, price in zip(sym_list, prices_list)}
    return {"prices": prices}
```