I want to detect if a JVM Class is a Kotlin class or not

I want to do special functionality if I encounter a Kotlin class as compared to a generic Java class. How can I detect if it is a Kotlin class?

I was hoping that calling someClass.kotlin would throw an exception or fail if the class wasn't Kotlin. But it wraps Java classes just fine. Then I noticed that if I do someClass.kotlin.primaryConstructor it seems to be null for all java classes even if they have a default constructor, is that a good marker? But can that return null for a Kotlin class as well?

What is the best way to say "is this a Kotlin class?"

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