code: public GeneralizedCounter<K> conditionalizeOnce(K o) {
      if (depth() < 1) {
        throw new RuntimeException("Error -- attempted to conditionalize a GeneralizedCounter of depth " + depth());
      } else {
        return conditionalizeHelper(o);
      }
    }
docs: Returns a GeneralizedCounter conditioned on the given top level object.
  This is just shorthand (and more efficient) for <code>conditionalize(new Object[] { o })</code>.