`iter()` doesn't require a "collection"

Documentation

The documentation for iter() says, for the one-argument form:

iter(iterable, /)

Return an iterator object. [...] the single argument must be a collection object which supports the iterable protocol (the __iter__() method), or it must support the sequence protocol (the __getitem__() method with integer arguments starting at 0). If it does not support either of those protocols, TypeError is raised.

This terminology is misleading, since a "collection" also needs to support size and containment checking. Per set and Collections Abstract Base Classes, respectively:

Like other collections, sets support x in set, len(set), and for x in set.

Collection : Sized, Iterable, Container : __contains__, __iter__, __len__

It should be possible to reword this section to avoid the term "collection", either by simply removing it or rephrasing the whole sentence.

Linked PRs

• gh-155857

組み込み関数のドキュメントにある、iter() の引数を 1 つ取る形式から始めます。iterable プロトコルと sequence プロトコルに関する文言を確認し、そのうえで “collection” という用語が削除または言い換えられ、サイズと包含のサポートを意味しないことを確認します。