Calculate a Score from Paired Values

Task

Write mean_absolute_error(expected, produced). It compares two lists of numbers position by position. For each pair, find the absolute difference abs(expected_value - produced_value). The score is the mean of all those differences.

Return a two-item tuple (score, status):

• if the lists have different lengths, return (None, "unequal lengths");
• if both lists are empty, return (None, "empty"); and
• otherwise, return (mean absolute difference, "ok").

The paired values are matched by their positions; do not reorder either list. Neither input list may be changed.

Example

The absolute differences are 1, 2, and 1, so their mean is (1 + 2 + 1) / 3, or 4 / 3. A mismatch is reported before any score is calculated:

Your implementation

Edit solution.py and keep this function name and signature:

Return exactly the required tuple and status strings. For a non-empty pair, score must be the arithmetic mean of the position-wise absolute differences; there is no rounding step. Equal empty lists are the one case that returns an "empty" status instead of a number. Do not print the result, ask for input, or mutate either list.