Waiting state: there are outstanding termination requests (i.e. context.stop(child) was called but the corresponding ChildTerminated() system message has not yet been processed). There could be no specific reason (UserRequested), we could be Restarting or Terminating. Removing the last child which was supposed to be terminating will return a different type of container, depending on whether or not children are left and whether or not the reason was "Terminating".

public class TerminatingChildrenContainer : ChildrenContainerBase

type TerminatingChildrenContainer =  
    class
        inherit ChildrenContainerBase
    end