How to fix pip error "SyntaxError: invalid syntax"?

Question

pip

I used pip and it prompted me to update the version, I did it and after that it writes this:

subcommand_name: Optional[str] = None
               ^ 
SyntaxError: invalid syntax

(in autocompletion.py file)
I downloaded pip-21.3.1.tar.gz from PyPI site and installed it, but it didn't help. There
was another error before, but I fixed it.

Answer 1

Found the answer on this site