sleep() in nodebox

I've been trying to use python's time.sleep(seconds) but I get the following error message:
'builtin_function_or_method' object has no attribute 'sleep'
can't I use sleep() in nodebox?
(and no, I didn't forget to 'import time')

Any ideas?

this should work

import time
time.sleep(2.5)
print time.clock()