API/BUG: freq retention in value_counts

[sanjanam1998]

• closes API/BUG: freq retention in value_counts #33830 (Replace xxxx with the GitHub issue number)
• Tests added and passed if fixing a bug or adding a new feature
• All code checks passed.
• Added type annotations to new arguments/methods/functions.
• Added an entry in the latest doc/source/whatsnew/v3.0.0.rst file if fixing a bug or adding a new feature.

[mroeschke]

Suggested change

	and hasattr(values, "freq")
	and values.freq is not None
	and hasattr(values, "freq")
	and values.freq is not None

Instead could you isinstance(values, DatetimeIndex) (you might need a local import of DatetimeIndex). Also you can use values.inferred_freq to get the frequency instead

[sanjanam1998]

Thanks for the suggestion. values.inferred_freq makes sense!
However, my assumption was that we want to make it more generic and not localise this fix to just DatetimeIndex. Please could you help me understand this?

[mroeschke]

DatetimeIndex is the only relevant object that requires frequency preservation, so it's OK to special case here

[sanjanam1998]

Got it!
I have also added TimedeltaIndex as that was one of the examples given in the issue for frequency preservation. Let me know if that makes sense.