IEnumerable <ContributorInvocation> BuildContributor(IPipelineContributor contributor)
 {
     _invocations = new List <ContributorInvocation>();
     _contributor = contributor;
     contributor.Initialize(this);
     if (_invocations.Count == 0)
     {
         _invocations.Add(new ContributorInvocation(contributor, Middleware.IdentitySingleTap));
     }
     CompleteKnownContributorDependencies(contributor);
     return(_invocations);
 }