I can't get RelativeBy to work for em with C#

I am unable to use a RelativeBy but this should be part of Selenium 4 and I am using the newest Appium. I Googled the below and it showed me what i was doing was correct but I am seeign an error.
IWebElement DuckFilterbox = _IOSdriver.FindElement(MobileBy.AccessibilityId(“Duck”));
IWebElement FilterField=_IOSdriver.FindElement(RelativeBy(MobileBy.Name(“Duck”)).LeftOf(DuckFilterbox));

Non-invocable member “RelativeBy” can not be used like a method