time.time() returns time as a float, but the conversion to float lose precision at the nanosecond resolution.

I propose to add a new time.time_ns() function which returns time as an integer number of nanoseconds since epoch. It's similar to the st_mtime_ns field of os.stat_result which extended the old st_mtime field.

For the full rationale, see my thread on python-ideas:
[Python-ideas] Add time.time_ns(): system clock with nanosecond resolution
https://mail.python.org/pipermail/python-ideas/2017-October/047318.html