In the test_01.py You can find the following code at line 78:
result = program.ex(**parameters) # what is returned by your function
-
self.assertEqual(type(result), list,
'il risultato prodotto deve essere una lista / '
f' the expected result should be a list (got {type(result)} instead)')
Ergo, the result should be a list
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But the images should be a tuple: (line 82)
if result:
self.assertEqual(type(result[0]), tuple,
'le immagini devono essere tuple / '
f'the image should be a tuple (got {type(result[0])} instead)')
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So the result should be a list of tuples