How does "bestTradeExactIn" returns value [PancakeSwap frontend]

Question

I was trying to understand how the token swap prices are determined in PancakeSwap by looking at codes and finally got to the point where best price is calculated based on some values.

The method is below:

    /**
 * Given a list of pairs, and a fixed amount in, returns the top `maxNumResults` trades that go from an input token
 * amount to an output token, making at most `maxHops` hops.
 * Note this does not consider aggregation, as routes are linear. It's possible a better route exists by splitting
 * the amount in among multiple routes.
 * @param pairs the pairs to consider in finding the best trade
 * @param currencyAmountIn exact amount of input currency to spend
 * @param currencyOut the desired currency out
 * @param maxNumResults maximum number of results to return
 * @param maxHops maximum number of hops a returned trade can make, e.g. 1 hop goes through a single pair
 * @param currentPairs used in recursion; the current list of pairs
 * @param originalAmountIn used in recursion; the original value of the currencyAmountIn parameter
 * @param bestTrades used in recursion; the current list of best trades
 */
static bestTradeExactIn(pairs: Pair[], currencyAmountIn: CurrencyAmount, currencyOut: Currency, { maxNumResults, maxHops }?: BestTradeOptions, currentPairs?: Pair[], originalAmountIn?: CurrencyAmount, bestTrades?: Trade[]): Trade[];

The code above is written in Trade Class. As far as I know, no process is written but it apparently returns some value where it is used like below:

const currentTrade: Trade | null =
      Trade.bestTradeExactIn(allowedPairs, currencyAmountIn, currencyOut, { maxHops: i, maxNumResults: 1 })[0] ??
      null
    console.log('currentTrade : ', currentTrade)

How come does "Trade.bestTradeExactIn(args...)" return value without any code for this method?

PancakeSwap frontend code : https://github.com/pancakeswap/pancake-frontend