def METHOD_NAME(seas, yr):
    if seas == "spring":
        return f"{yr}-06-01"
    if seas == "summer":
        return f"{yr}-09-01"
    if seas == "autumn":
        return f"{yr}-12-01"
    if seas == "winter":
        return f"{yr}-03-01"
    if seas == "all":
        return f"{yr}-01-01"
    raise ValueError("Invalid input for season (seas):", seas)