code: private boolean addChineseIndexCharacters() {
          UnicodeSet contractions = new UnicodeSet();
          try {
              collatorPrimaryOnly.internalAddContractions(BASE.charAt(0), contractions);
          } catch (Exception e) {
              return false;
          }
          if (contractions.isEmpty()) { return false; }
          initialLabels.addAll(contractions);
          for (String s : contractions) {
              assert(s.startsWith(BASE));
              char c = s.charAt(s.length() - 1);
              if (0x41 <= c && c <= 0x5A) {  // A-Z
                  // There are Pinyin labels, add ASCII A-Z labels as well.
                  initialLabels.add(0x41, 0x5A);  // A-Z
                  break;
              }
          }
          return true;
      }
docs: Add Chinese index characters from the tailoring.