>>> from suavitza import suavitza_serie

--ini-enunciat

>>> it = iter([3, 5, 1])
>>> it2 = suavitza_serie(it)
>>> next(it2)
3
>>> next(it2)
4
>>> next(it2)
5
>>> for x in it2:
...    print(x, end=',')
4,3,2,1,

>>> for x in suavitza_serie(iter([1, 3, 4, 7, 8, 7, 3, 1, 1, 8, 12])):
...    print(x, end=',')
1,2,3,4,5,6,7,8,7,6,5,4,3,2,1,1,2,3,4,5,6,7,8,9,10,11,12,

--fi-enunciat

>>> it = suavitza_serie(iter([3, 2, 2, 3, -5, -5, -2]))
>>> for x in it:
...    print(x, end=',')
3,2,2,3,2,1,0,-1,-2,-3,-4,-5,-5,-4,-3,-2,
>>> it = suavitza_serie(iter([3, 2, 2, 3, -5, -5, -2]))
>>> it = suavitza_serie(it)
>>> for x in it:
...    print(x, end=',')
3,2,2,3,2,1,0,-1,-2,-3,-4,-5,-5,-4,-3,-2,
>>> for x in suavitza_serie(iter([2, 1, 2, 7, -3, 0, 1, 5, -1])):
...    print(x, end=',')
2,1,2,3,4,5,6,7,6,5,4,3,2,1,0,-1,-2,-3,-2,-1,0,1,2,3,4,5,4,3,2,1,0,-1,