Where is the documentation for NSConcreteAttributedString?

Where is Apple's documentation of NSConcreteAttributedString?

I need to get the String from NSExtensionItem.attributedContentText property, which is of type NSConcreteAttributedString.

Ok. I found the string instance property of the class.

I would like to see documentation for that anyhow. Anyone know why it's not in Apple Developer Documentation?

Because it's an private class of the NSAttributeString class cluster, and there shouldn't be any difference in the public interface.

Where is the documentation for NSConcreteAttributedString?
 
 
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