def predecessors(self, dest):
        """
        Yield (node, data) pairs representing the predecessors of node *dest*.
        (*data* will be None if no data was specified when adding the edge)
        """
        for src in self._preds[dest]:
            yield src, self._edge_data[src, dest]

        Yield (node, data) pairs representing the predecessors of node *dest*.
        (*data* will be None if no data was specified when adding the edge)
        
numba/core/controlflow.py