code: public static String unexpand(CharSequence self, int tabStop) {
          String s = self.toString();
          if (s.length() == 0) return s;
          try {
              StringBuilder builder = new StringBuilder();
              for (String line : readLines((CharSequence) s)) {
                  builder.append(unexpandLine(line, tabStop));
                  builder.append("\n");
              }
              // remove the normalized ending line ending if it was not present
              if (!s.endsWith("\n")) {
                  builder.deleteCharAt(builder.length() - 1);
              }
              return builder.toString();
          } catch (IOException e) {
              /* ignore */
          }
          return s;
      }
docs: Replaces sequences of whitespaces with tabs.
  
  @param self A CharSequence to unexpand
  @param tabStop The number of spaces a tab represents
  @return an unexpanded String
  @since 1.8.2