Fixed mypy errors in frequencies.py (#47644)
Fixed mypy errors in frequencies.py (#47644)

* TST: Added test for consistent type with unique agg #22558

* TST: Added test for consistent type with unique agg #22558

* TST: Moved and restructured test #22558

* TYP: Fixed mypy issues in frequencies

* TYP: Removed accidental inclusion

Co-authored-by: Steven Rotondo <ab85dc231737c71f924d3824254eb8e5e2bb889e@gmail.com>
pandas-dev/pandas,pandas-dev/pandas,datapythonista/pandas,pandas-dev/pandas,pandas-dev/pandas,datapythonista/pandas,datapythonista/pandas,datapythonista/pandas