code: public void end() {
          if (endCallback != null) {
              endCallback.accept(this, context);
          }
  
          if (currentPrompt != null) {
              currentPrompt.conversationEnded(context);
              currentPrompt = null;
          }
  
          Extensions.get(context.getBot(), ConversationRegistry.class).removeConversation(this);
          virgin = false;
      }
docs: Calls the conversation end method of the current prompt, and removes conversation
  from registry.
  
  @see ConversationPrompt#conversationEnded(ConversationContext)