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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def format_year(year):
 """ Format the year value of the ``YearArchiveView``, which can be a integer or date object. This tag is no longer needed, but exists for template compatibility. It was a compatibility tag for Django 1.4. """

    if isinstance(year, (date, datetime)):
        # Django 1.5 and up, 'year' is a date object, consistent with month+day views.
        return unicode(year.year)
    else:
        # Django 1.4 just passes the kwarg as string.
        return unicode(year)