def getValuesForProperty(self, aPropURIRef):
        """
        generic way to extract some prop value eg
            In [11]: c.getValuesForProperty(rdflib.RDF.type)
            Out[11]:
            [rdflib.term.URIRef(u'http://www.w3.org/2002/07/owl#Class'),
             rdflib.term.URIRef(u'http://www.w3.org/2000/01/rdf-schema#Class')]
        """
        if not type(aPropURIRef) == rdflib.URIRef:
            aPropURIRef = rdflib.URIRef(aPropURIRef)
        return list(self.rdflib_graph.objects(None, aPropURIRef))