Static AVAudioSessionSilenceSecondaryAudioHintTypeKey 

pub unsafe static AVAudioSessionSilenceSecondaryAudioHintTypeKey: &'static NSString

Available on crate feature AVAudioSession only.

keys for AVAudioSessionSilenceSecondaryAudioHintNotification value is an NSNumber representing an AVAudioSessionSilenceSecondaryAudioHintType

See also Apple’s documentation