How to convert `std.datetime.Duration` to seconds of floating point type?

[drug via Digitalmars-d-learn]

Now I do it this way (https://run.dlang.io/is/8kVibT):
```
        auto some_duration = dur!"msecs"(500);
        auto seconds = some_duration.total!"hnsecs" / 10_000_000.0;
        assert(seconds.approxEqual(0.5));
```
is there better way to do it?

Thanks in advance