timeit error in example convolve.py

When I run the convolve.py

I met a error with timeit function
I will get sample_time= 0 after sample_trials=3.So It will bring a ZeroDivisionError.

Start by running the convolve.py example and inspect its timeit usage around sample_time and sample_trials. Confirm the example no longer reaches a ZeroDivisionError when sample_time is 0 and that it reports a valid timing result.

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