How to use the aniso8601.resolution.DateResolution.Ordinal function in aniso8601

if len(datestrsplit) == 3:
        if len(datestrsplit[0]) == 4 and len(datestrsplit[1]) == 2 and len(datestrsplit[2]) == 2:
            return DateResolution.Day

    #Check case 2
    if len(isodatestr) == 8 and isodatestr.find('-') == -1:
        return DateResolution.Day

    #An ISO string may be a ordinal date representation if:
    # 1) When split on a hyphen, the sizes of the parts are 4, 3
    # 2) There are no hyphens, and the length is 7

    #Check case 1
    if len(datestrsplit) == 2:
        if len(datestrsplit[0]) == 4 and len(datestrsplit[1]) == 3:
            return DateResolution.Ordinal

    #Check case 2
    if len(isodatestr) == 7 and isodatestr.find('-') == -1:
        return DateResolution.Ordinal

    #None of the date representations match
    raise ValueError('String is not an ISO 8601 date, perhaps it represents a time or datetime.')