import tensorflow.contrib.graph_editor as ge

            if d_xs_new[j] is not None:
                if d_xs[j] is None:
                    d_xs[j] = _unsparsify(d_xs_new[j])
                else:
                    d_xs[j] += _unsparsify(d_xs_new[j])


    return d_xs

def tf_toposort(ts, within_ops=None):
    all_ops = ge.get_forward_walk_ops([x.op for x in ts], within_ops=within_ops)

    deps = {}
    for op in all_ops:
        for o in op.outputs:
            deps[o] = set(op.inputs)
    sorted_ts = toposort(deps)

    # only keep the tensors from our original list
    ts_sorted_lists = []
