> I think that one of available types of time values returned by os.stat() should
> allow to directly pass these values to os.futimens() and os.utimensat(), which
> expect (time_sec, time_nsec) tuples.

If we choose to give the possibility to get decimal.Decimal objects,
we should also patch some functions to support Decimal objects, like
datetime.datetime.fromtimestamp() (today, it "just works", because a
Decimal object can be converted to float). We may accept Decimal in
os.futimens() and os.utimensat(), but I am not sure for this
particular case.

To come back to my format solution, we can also support classical C
structures to interact with C functions (in Python or more directly
using ctypes):
 - "timeval": (secs, usec) where sec and usec are int
 - "timespec": (secs, nsec) where sec and nsec are int

Or we may introduce conversion functions from other types like float,
Decimal or another type.