[docs] [issue33774] Document that @lru_cache caches based on exactly how the function arguments are specified

[Raymond Hettinger]

Change by Raymond Hettinger <raymond.hettinger at gmail.com>:


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keywords: +patch
pull_requests: +8727
stage: needs patch -> patch review

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue33774>
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