Thanks a lot for the clarification, I get it now (I think).

> 2. _HashedSeq is only used as a key in a dictionary. When you look up a key in dictionary, it compares hashes first. __eq__ is only called when hashes match.

I was looking at the docs [1] and [2] and didn't come across this.
For me, this explanation of how __hash__ and __eq__ are used in the LRU cache would have been helpful to read in [1], but of course there is a tradeoff in how long to make docstrings.
If it is already explained somewhere else in the docs, linking to that place from [1] could be useful.

[1] https://docs.python.org/3/library/functools.html#functools.lru_cache
[2] https://docs.python.org/3/reference/datamodel.html#object.__hash__