Using the tests, we are not picking up when a method has not been typed.
For example, in line 799 of test_frame.py, we have:

    df = pd.concat([s1, s2], axis=1)

If you turn on the pyright option "reportUnknownVariableType": true for pyright, we get a report that says:

tests\pandas\test_frame.py:799:5 - error: Type of "df" is unknown (reportUnknownVariableType)

In addition, we get a bunch of reports like this:

tests\pandas\test_frame.py:85:5 - error: Type of "s" is partially unknown
    Type of "s" is "Series[Unknown]" (reportUnknownVariableType)

which I think is fine. I created an issue for pyright to see if we can differentiate the two different kinds of errors. microsoft/pyright#3066

For @gramster to consider - how do we make it so we know which things are missing in the partial stubs?