delegate = newDelegate;
        }
      }
    }

    /**
     * If collection is empty, remove it from {@code AbstractMapBasedMultimap.this.map}. For
     * subcollections, check whether the ancestor collection is empty.
     */
    void removeIfEmpty() {
      if (ancestor != null) {
        ancestor.removeIfEmpty();
      } else if (delegate.isEmpty()) {
        map.remove(key);

          delegate = newDelegate;
        }
      }
    }

    /**
     * If collection is empty, remove it from {@code AbstractMapBasedMultimap.this.map}. For
     * subcollections, check whether the ancestor collection is empty.
     */
    void removeIfEmpty() {
      if (ancestor != null) {
        ancestor.removeIfEmpty();
      } else if (delegate.isEmpty()) {
        map.remove(key);