>>> from cerca_llistes import index_llista

>>> index_llista([3, 12, 10, 8, 12], 12)
1
>>> index_llista([3, 12, 10, 8, 12], 5)
-1
>>> index_llista([5, -9, 15, 1, 34, 6], 34)
4
>>> index_llista(['bar', 'cel', 'ona'], 'bar')
0
>>> index_llista([], 4)
-1