return obj != null && removeFromColumnIf(Maps.<V>valuePredicateOnEntries(equalTo(obj)));
      }

      @Override
      public boolean removeAll(Collection<?> c) {
        return removeFromColumnIf(Maps.<V>valuePredicateOnEntries(in(c)));
      }

      @Override
      public boolean retainAll(Collection<?> c) {
        return removeFromColumnIf(Maps.<V>valuePredicateOnEntries(not(in(c))));
      }