code: public HString leftContext(@NonNull AnnotationType type, int windowSize) {
        windowSize = Math.abs(windowSize);
        Preconditions.checkArgument(windowSize >= 0);
        int sentenceStart = sentence().start();
        if (windowSize == 0 || start() <= sentenceStart) {
           return Fragments.detachedEmptyHString();
        }
        HString context = firstToken().previous(type);
        for (int i = 1; i < windowSize; i++) {
           HString next = context
                             .firstToken()
                             .previous(type);
           if (next.end() <= sentenceStart) {
              break;
           }
           context = context.union(next);
        }
        return context;
     }
docs: Left context h string.
  
  @param type       the type
  @param windowSize the window size
  @return the h string