['2023-01-01', '2023-01-31', '2023-02-01', '2023-02-28']))
        >>> ser
        2023-01-01    1
        2023-01-31    2
        2023-02-01    3
        2023-02-28    4
        dtype: int64
        >>> ser.resample('MS').asfreq()
        2023-01-01    1
        2023-02-01    3
        Freq: MS, dtype: int64
        rŅ