docs: public static SoyValue plus(SoyValue operand0, SoyValue operand1) {
      if (operand0 instanceof IntegerData && operand1 instanceof IntegerData) {
        return IntegerData.forValue(operand0.longValue() + operand1.longValue());
      } else if (operand0 instanceof NumberData && operand1 instanceof NumberData) {
        return FloatData.forValue(operand0.numberValue() + operand1.numberValue());
      } else {
        // String concatenation is the fallback for other types (like in JS). Use the implemented
        // coerceToString() for the type.
        return StringData.forValue(operand0.coerceToString() + operand1.coerceToString());
      }
    }