The __setslice__ method
__setslice__(self, i, j, sequence)
Called to implement assignment to
self[i:j]. Same notes for i and j
as for __getslice__().
This method is deprecated. If no __setslice__() is found, or for
extended slicing of the form
self[i:j:k], a slice object is
created, and passed to __setitem__(), instead of
__setslice__() being called.