docs: public CoverageByTime withGroups(ReservationCoverageGroup... groups) {
          if (this.groups == null) {
              setGroups(new java.util.ArrayList<ReservationCoverageGroup>(groups.length));
          }
          for (ReservationCoverageGroup ele : groups) {
              this.groups.add(ele);
          }
          return this;
      }