code: private Set<URI> listEntitesWithModelReference(URI entityType, URI modelReference) {
          Set<URI> entities = ImmutableSet.of();
          // Deal with services
          if (entityType.toASCIIString().equals(MSM.Service.getURI())) {
              entities = this.serviceManager.listServicesWithModelReference(modelReference);
          } else if (entityType.toASCIIString().equals(MSM.Operation.getURI())) {
              entities = this.serviceManager.listOperationsWithModelReference(modelReference);
          }
          return entities;
      }
docs: Generic implementation for finding all the Services or Operations that have one specific model reference.
  
  @param entityType     the MSM URI of the type of entity we are looking for. Only supports Service and Operation.
  @param modelReference the model reference URI we are looking for.
  @returns a Set of URIs of matching services/operations. Note that this method makes no use of reasoning and therefore
  the match will always be exact in this case.