docs: public boolean contains(ReadableInterval interval) {
          if (interval == null) {
              return containsNow();
          }
          long otherStart = interval.getStartMillis();
          long otherEnd = interval.getEndMillis();
          long thisStart = getStartMillis();
          long thisEnd = getEndMillis();
          return (thisStart <= otherStart && otherStart < thisEnd && otherEnd <= thisEnd);
      }