`dict.fromkeys` must mark its parameters as pos-only

[sobolevn]

Bug report

Here's how it looks now:

From this defitinion I undertand that I can pass value as a named keyword, but I can't:

>>> dict.fromkeys(x, value=0)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: dict.fromkeys() takes no keyword arguments

>>> import inspect
>>> inspect.signature(dict.fromkeys)
<Signature (iterable, value=None, /)>

I just made this error in a real code: wemake-services/wemake-python-styleguide#2994

Many other definitions in this file use / to properly mark positional only parameters. Like:

and etc.

So, I will send a PR to add / to dict.fromkeys

Linked PRs

• gh-121196: Document dict.fromkeys params as pos-only #121197
• [3.13] gh-121196: Document dict.fromkeys params as pos-only (GH-121197) #121242
• [3.12] gh-121196: Document dict.fromkeys params as pos-only (GH-121197) #121243