def subjects(self, predicate=None, object=None):
        for s, p, o in self.triples((None, predicate, object)):
            yield s
method to return data for the various display roles in qt
dataset/ETHPy150Open RDFLib/rdflib/rdflib/graph.py/Graph.subjects--crossover with--dataset/ETHPy150Open shotgunsoftware/pyqt-uploader/uploader.py/ShotgunFileModel.data