public bool OnProjectRemoved(IEnumerable <StateSet> stateSets, ProjectId projectId)
            {
                var removed = false;

                foreach (var stateSet in stateSets)
                {
                    removed |= stateSet.OnProjectRemoved(projectId);
                }

                _projectStates.RemoveStateSet(projectId);
                return(removed);
            }
 /// <summary>
 /// Remove given <see cref="ProjectId"/>.
 /// </summary>
 public void RemoveStateSet(ProjectId projectId)
 {
     _projectStates.RemoveStateSet(projectId);
 }