[docs] [issue19362] Documentation for len() fails to mention that it works on sets

[Terry J. Reedy]

Changes by Terry J. Reedy <tjreedy at udel.edu>:


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resolution:  -> fixed
stage:  -> resolved
status: open -> closed
versions: +Python 2.7, Python 3.5

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue19362>
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