def METHOD_NAME(
    self,
    instrument_id: InstrumentId,
    ts_init: int,
) -> OrderBookDeltas:
    bids = [
        BookOrder(OrderSide.BUY, Price.from_str(o.price), Quantity.from_str(o.size), 0)
        for o in self.bids
    ]
    asks = [
        BookOrder(OrderSide.SELL, Price.from_str(o.price), Quantity.from_str(o.size), 0)
        for o in self.asks
    ]
    deltas = [OrderBookDelta.clear(instrument_id, ts_init, ts_init, self.lastUpdateId)]
    deltas += [
        OrderBookDelta(
            instrument_id,
            BookAction.ADD,
            o,
            ts_init,
            ts_init,
            sequence=self.lastUpdateId,
        )
        for o in bids + asks
    ]
    return OrderBookDeltas(instrument_id=instrument_id, deltas=deltas)