docs: function rollback(numVersions) {
              var snapshotsLength = this.$$snapshots ? this.$$snapshots.length : 0;
              numVersions = Math.min(numVersions || 1, snapshotsLength);
  
              if (numVersions < 0) {
                  numVersions = snapshotsLength;
              }
  
              if (snapshotsLength) {
                  this.rollbackTo(this.$$snapshots.length - numVersions);
              }
  
              return true;
          }