         }
 
         guard let newDescriptor = descriptor.withSymbolicTraits(newTraits) else {
+            assertionFailure("Unable to modify Font's Traits: \(self)")
             return self
         }
 

    /// - Returns: A new UIFont with the same descriptors as the current instance, but with its traits updated, as specified.
    ///
    func modifyTraits(_ traits: UIFontDescriptorSymbolicTraits, enable: Bool) -> UIFont {
        let descriptor = shouldUseDefaultDescriptor() ? defaultFontDescriptor : fontDescriptor
        var newTraits = descriptor.symbolicTraits

        if enable {

        return fontDescriptor.symbolicTraits.contains(traits)
    }
}
