How to access function of companion object using class object in Kotlin?

Question

In Kotlin, we can access function or property of companion object using class name as following:

class DemoClass {
    companion object {
        fun someFunction() {}
    }
}

// Accessing function
DemoClass.someFunction()

But how can I access the same function if I have an object of DemoClass?

class DemoClass {
    companion object {
        fun someFunction() {}
    }
}

val demoObj = DemoClass()

// I cannot do following - It will not compile.
demoObj.someFunction() 

Basically, I want to access companion function using class object.