SYNOPSIS
str = tostring(time)
DESCRIPTION
A time in string context returns the time formatted as per ISO 8601 extended format.
RETURN VALUE
A string formatted as "HH:MM:SS", with the hours formatted in 24h mode.
If time is not valid, returns the string "??:??:??".
ERRORS
Raises an error if time is not a time instance.
EXAMPLE
>
>
t = clock.currentTime()
print (t)
11:16:41