code: protected MultiStringWrapper asMultiStringWrapper(StringWrapper w) 
  	{
  		if (w instanceof MultiStringWrapper) return (MultiStringWrapper)w;
  		else 	{
  			MultiStringWrapper mw = new MultiStringWrapper( w.unwrap(), innerLearners.length, delim);
  			for (int i=0; i<mw.size(); i++) {
  				mw.set(i, prepareForLearner( mw.get(i), innerLearners[mw.getDistanceLearnerIndex(i)] ) );
  			}
  			return mw;
  		}
  	}
docs: /* lazily convert to a MultiStringWrapper