code: public String getSelectorString() {
          StringBuilder sb = new StringBuilder();
          for (List<String> selector : selectors) {
              if (sb.length() > 0) {
                  sb.append(",");
              }
              for (String s : selector) {
                  if (sb.length() > 0) {
                      sb.append(" ");
                  }
                  sb.append(s);
              }
          }
          return sb.toString();
      }
docs: Compiles the effective selector string.
  
  @return a string containing all selector chains for this section