@protocol GADRTBAdapter <GADMediationAdapter>
Adapter that provides signals to the Google Mobile Ads SDK to be included in an auction.
Returns an initialized RTB adapter.
- (nonnull instancetype)init;
Asks the receiver for secure signals. Signals are provided to the 3PAS at request time. The receiver must call completionHandler with signals or an error.
This method is called on a non-main thread. The receiver should avoid using the main thread to prevent signal collection timeouts.