What are convenience required initializers in Swift?

Question

I saw in this answer that the user specifies a convenience required init(). What exactly does this mean?

I understand that the required key

Answer 1

Declaring required initialiser of class as convenience lets subclasses easily inherit it and thus ommit its implementation

protocol P {
    var some: Int! {get}
    init(some: Int)
}

class C: P {
    private(set) var some: Int!
    convenience required init(some: Int) {
        self.init()
        self.some = some
    }
}

class D: C {
    // no need in required init(some: Int)...
}