TYP: Fix chainmap typing for mypy 0.740+

[xhochy]

This will otherwise raise a failure during a mypy update. Also increase type precision of this file to 100%.

• closes #xxxx
• tests added / passed
• passes black pandas
• passes git diff upstream/master -u -- "*.py" | flake8 --diff
• whatsnew entry

cc @simonjayhawkins

[jreback]

cc @simonjayhawkins

[jreback]

note we are currently pinned to 0.73 for a number of issues.

[xhochy]

note we are currently pinned to 0.73 for a number of issues.

Yes, I'm aware of them and this a tiny step to get rid of them.

[jreback]

note we are currently pinned to 0.73 for a number of issues.

Yes, I'm aware of them and this a tiny step to get rid of them.

great that's what I figured, thanks!

[topper-123]

PR looks good to me.

There has been a build-in collections.ChainMap since python 3.3. Is this version different or could we switch over to the builtin version?

[xhochy]

PR looks good to me.

There has been a build-in collections.ChainMap since python 3.3. Is this version different or could we switch over to the builtin version?

The typing one used here is simply a typed alias for it that exists since Python 3.6.

[simonjayhawkins]

@xhochy lgtm. Thanks for the PR.

[simonjayhawkins]

note we are currently pinned to 0.73 for a number of issues.

This will help for 0.73 too...

#30539 pandas\compat\chainmap.py:4: error: Implicit generic "Any". Use "typing.ChainMap" and specify generic parameters

[jreback]

thanks @xhochy