docs: public static String releaseBuilder(StringBuilder sb) {
          Validate.notNull(sb);
          String string = sb.toString();
  
          if (sb.length() > MaxCachedBuilderSize)
              sb = new StringBuilder(MaxCachedBuilderSize); // make sure it hasn't grown too big
          else
              sb.delete(0, sb.length()); // make sure it's emptied on release
  
          synchronized (builders) {
              builders.push(sb);
  
              while (builders.size() > MaxIdleBuilders) {
                  builders.pop();
              }
          }
          return string;
      }