def todo(vals: Sequence[TfVal]):
    trace = TensorFlowTrace(main, core.cur_sublevel())
    return [TensorFlowTracer(trace, v, out_tracer.aval) for (v, out_tracer) in util.safe_zip(vals, out_tracers)]
def todo(vals: Sequence[TfVal]):
    trace = TensorFlowTrace(main, core.cur_sublevel())
    return [TensorFlowTracer(trace, v, out_tracer.aval) for (v, out_tracer) in util.safe_zip(vals, out_tracers)]