Error in the task or asserts

Hi! I would like to give some feedback about Mission Number Length

From: https://py.checkio.org/mission/number-length/solve/

The task says: "You have a positive integer. Try to find out how many digits it has? Input: A positive Int Output: An Int."

In the asserts we see:

Line 20: assert number_length(0) == 1

Zero is not a positive integer! Or the task is meant for non-negative integers?

Best regards

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