public static IUriNode GetRestrictionProperty(this OntologyClass oClass)
{
if (!oClass.HasRestrictionProperty())
{
throw new RdfException($"Ontology class {oClass} does not have a restriction property.");
}
IUriNode onProperty = oClass.Graph.CreateUriNode(VocabularyHelper.OWL.onProperty);
return oClass.GetNodesViaProperty(onProperty).UriNodes().First(node => node.IsOntologyProperty());
}