code: func (sv SupportedVersions) NextVersionPair(current *EtcdVersionPair) *EtcdVersionPair {
  	nextVersion := sv.NextVersion(current.version)
  	if nextVersion == nil {
  		return nil
  	}
  	storageVersion := storageEtcd3
  	if nextVersion.Major == 2 {
  		storageVersion = storageEtcd2
  	}
  	return &EtcdVersionPair{version: nextVersion, storageVersion: storageVersion}
  }
docs: // NextVersionPair returns the next supported version after the given current version and infers
  // the storage version from the major version part of the next version.