from enum import Enum


class Vintage(Enum):
    """
    Enum for valid census years
    """
    CENSUS_2021 = 2021  # Census 2021
    # CENSUS_2016 = 2016  # Census 2016
    # CENSUS_2011 = 2011  # Census 2011
    # CENSUS_2006 = 2006  # Census 2006
    # CENSUS_2001 = 2001  # Census 2001
    # CENSUS_1996 = 1996  # Census 1996
    # CENSUS_1991 = 1991  # Census 1991
    # CENSUS_1986 = 1986  # Census 1986
    # CENSUS_1981 = 1981  # Census 1981
    # CENSUS_1976 = 1976  # Census 1976

    def __str__(self) -> str:
        """
        String representation of the Vintage enum.
        
        Returns
        -------
        str
            The string representation of the vintage year.
        """
        return f'{self.value:04d}'