[issue21257] Document parse_headers function of http.client

[Ashwin Ramaswami]

Change by Ashwin Ramaswami <aramaswamis at gmail.com>:


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keywords: +patch
pull_requests: +10888
stage: needs patch -> patch review

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue21257>
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