code: public static BitfinexOrderBookSymbol rawOrderBook(final String currency, final String profitCurrency) {
          final String currencyNonNull = Objects.requireNonNull(currency).toUpperCase();
          final String profitCurrencyNonNull = Objects.requireNonNull(profitCurrency).toUpperCase();
          
          return rawOrderBook(BitfinexCurrencyPair.of(currencyNonNull, profitCurrencyNonNull));
      }
docs: Returns symbol for raw order book channel
  
  @param currency       of raw order book channel
  @param profitCurrency of raw order book channel
  @return symbol