An event bus written in Kotlin using RxJava

NetworkBus.kt

import rx.Observable
import rx.Subscription
import rx.subjects.PublishSubject
import rx.subjects.SerializedSubject
import rx.subscriptions.CompositeSubscription

object EventBus {

    val bus = SerializedSubject(PublishSubject.create<Any>())

    private val subscriptions = mutableMapOf<Any, CompositeSubscription>()

    fun send(event: Any) {
        bus.onNext(event)
    }

    inline fun <reified T : Any> observe(): Observable<T> = bus.ofType(T::class.java)

    fun unregister(subscriber: Any) {
        val compositeSubscription = subscriptions[subscriber] ?: return

        compositeSubscription.clear()
        subscriptions.remove(subscriber)
    }

    fun register(subscriber: Any, subscription: Subscription) {
        val compositeSubscription = subscriptions[subscriber] ?: CompositeSubscription()

        compositeSubscription.add(subscription)
        subscriptions[subscriber] = compositeSubscription
    }

}

fun Subscription.register(subscriber: Any) {
    NetworkBus.register(subscriber, this)
}

Is this RxJava 1 or 2?