adcolony

I'm trying to add AdColony mediation into AdMob. I follow the instructions from 'https://developers.google.com/admob/ios/mediation/adcolony'. After pod 'GoogleMobileAdsMediationAdColony', I open Xcode to test my app and get a link error: Undefine symbol: '_OBJC_CLASS_$_SKAdImpression' as well as a warning: Could not find…