A computed observable provides the following functions:
dispose(): This manually disposes the computed observable, clearing all subscriptions to dependencies. This function is useful if you want to stop a computed observable from being updated or want to clean up memory for a computed observable that has dependencies on observables that won't be cleaned.
extend(extenders): This applies the given extenders to the computed observable.
getDependenciesCount(): This returns the current number of dependencies of the computed observable.
getSubscriptionsCount(): This returns the current number of subscriptions (either from other computed observables or manual subscriptions) of the computed observable.
isActive(): This returns whether ...