<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def timeit(output):
 """ If output is string, then print the string and also time used """

    b = time.time()
    yield
    print output, 'time used: %.3fs' % (time.time()-b)