import uuid
from datetime import datetime
from typing import Dict, List, Optional


class ExampleService:
    def __init__(self):
        self._store: Dict[str, dict] = {}

    async def list_all(self) -> List[dict]:
        return list(self._store.values())

    async def get_by_id(self, example_id: str) -> Optional[dict]:
        return self._store.get(example_id)

    async def create(self, data: dict) -> dict:
        example_id = str(uuid.uuid4())
        item = {
            "id": example_id,
            "created_at": datetime.utcnow().isoformat(),
            **data,
        }
        self._store[example_id] = item
        return item