Potential New Check: has_n_values

[ZaxR]

    def has_n_values(df, items):
        """Has exactly n unique values in specified columns."""
        cols_n_unique = {col: df[col].nunique() for col in list(items.keys())}
        bad_cols = [col for col, n_unique in items.items() if cols_n_unique[col] != n_unique]

        if bad_cols:
            raise AssertionError(f"The following columns have a different number of unique items than expected: "
                                 f"{', '.join(bad_cols)}")

[ZaxR]

Can use the following for the tests: pandas-dev/pandas#28202