code: public final void addCloseListener(@NonNull final CloseListener listener) {
          Condition.INSTANCE.ensureNotNull(listener, "The listener may not be null");
          listeners.add(listener);
      }
docs: Adds a new listener, which should be notified, when the chip has been closed.
  
  @param listener
  The listener, which should be added, as an instance of the type {@link
  CloseListener}. The listener may not be null