insort_left and insort_right rebound `x` to `key(x)` and then handed that
same value to both the search and `a.insert`, so the object the caller
passed in never reached the list:
>>> words = ["a", "ccc"]
>>> bisect.insort(words, "bb", key=len)
>>> words
['a', 2, 'ccc']
The key now feeds the search only, and the insert keeps the original.
Assisted-by: Claude Code:claude-opus-5
