feat: use walrus operator instead of match and if

[vlopezferrando]

Use the walrus operator for snippets with the pattern:

# Convert this:
math = re.match(regex):
if match:
   ...

# To this:
if math := re.match(regex):
   ...

Limitations:

• If the match function is imported with an alias (e.g. from re import match as m), it will not be transformed.
• When re.match is used, we do not check that re comes from import re.

[morgante]

We should not have these sorts of snippets in descriptions. This is actually the exact point of the samples embedded in the markdown.

You can move this down below as the first sample for this pattern, and that will make it automatically tested.

[morgante]

It's often easier to look at individual before/after pairs. I'd consider spitting this into multiple samples.

[vlopezferrando]

Done, I've split all test cases.

[morgante]

Not sure I follow the difference here. Either way please resolve this todo and avoid commented out code.

[vlopezferrando]

I've removed the comment. I was thinking of double-checking that re is an imported module and not something else, but I guess it's nitpicking.