and isinstance(update_dict[key], list)
        ):
            main_dict[key] = main_dict[key] + update_dict[key]
        else:
            main_dict[key] = value


def get_value_or_default(
    first_item: DefaultPlaceholder | DefaultType,
    *extra_items: DefaultPlaceholder | DefaultType,
) -> DefaultPlaceholder | DefaultType:
    """
    Pass items or `DefaultPlaceholder`s by descending priority.

    EventSourceResponse,
    ServerSentEvent,
    format_sse_event,
)
from fastapi.types import DecoratedCallable, IncEx
from fastapi.utils import (
    create_model_field,
    generate_unique_id,
    get_value_or_default,
    is_body_allowed_for_status_code,
)
from starlette import routing
from starlette._exception_handler import wrap_app_handling_exceptions
from starlette._utils import is_async_callable