http://docs.python.org/3/reference/datamodel.html says:
> Sequences also support slicing:
a[i:j] selects all items with index
k such
that
i <= k < j. When used as an expression, a slice is a
sequence of the same type. This implies that the index set is renumbered so
that it starts at 0.
But I think this sentence explains about standard types and not definition of sequence.
And collections.abc.Sequence requires "index()" and "count()".
What is the requirement for calling something is "sequence"?
Off Topc: Sequence.__iter__ uses __len__ and __getitem__ but default iterator uses only __getitem__. This difference is ugly.