Function load_state_ids 

async fn load_state_ids(
    services: &Services,
    room_id: &RoomId,
    state_at: &EventId,
    sender_user: &UserId,
    bypass_visibility: bool,
) -> Result<Vec<(ShortStateKey, OwnedEventId)>>

Loads the room state at the event that anchors the response’s state.

An anchor without recorded state, such as a room’s create event or a backfilled event, falls back to the state fallback_shortstatehash selects for the requester, which may be none.