def computeGraphHeads(self):
        graphHeads = filter(lambda n: self.unfinished_pred_counts[n] == 0,
                            self.G.nodes_iter())
        logger.info("Graph heads: " + str(graphHeads))
        return graphHeads # TODO call \ix -> self.enqueue ix on these
adds stages with no incomplete predecessors to the runnable queue
dataset/ETHPy150Open Mouse-Imaging-Centre/pydpiper/pydpiper/pipeline.py/Pipeline.computeGraphHeads