code: public static long getDurationFromPeriod(Every every) {
          if (!Strings.isNullOrEmpty(every.value())) {
              return toDuration(PERIOD_FORMATTER.parsePeriod(every.value()));
          }
          return -1;
      }
docs: Parses the given String as a period and returns the number of seconds.
  The given String must follows this syntax: XdYhZmTs.
  
  @param every the period to parse
  @return the parsed period in seconds, -1 if there are no period