docs: public void logPurchase(BigDecimal purchaseAmount, Currency currency, Bundle parameters) {
  
          if (purchaseAmount == null) {
              notifyDeveloperError("purchaseAmount cannot be null");
              return;
          } else if (currency == null) {
              notifyDeveloperError("currency cannot be null");
              return;
          }
  
          if (parameters == null) {
              parameters = new Bundle();
          }
          parameters.putString(AppEventsConstants.EVENT_PARAM_CURRENCY, currency.getCurrencyCode());
  
          logEvent(AppEventsConstants.EVENT_NAME_PURCHASED, purchaseAmount.doubleValue(), parameters);
          eagerFlush();
      }