[docs] a doc bug in itertools.islice

[王迪]

Hi!
I found a bug in https://docs.python.org/3/library/itertools.html, where the argument should be “seq, start, [stop, step].”which makes me puzzled for the example.
[cid:image001.png at 01D3C071.391FD020]
Thanks.
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Best regards，
Andy Wang


E-mail:   wangdi03 at ppdai.com
Website:  www.ppdai.com<http://www.ppdai.com>


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