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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 get_redirect_url(self, **kwargs):
 """ Redirect to request parameter 'next' or to referrer if url is not defined. """

        if self.request.REQUEST.has_key('next'): 
            return self.request.REQUEST.get('next')
        url = RedirectView.get_redirect_url(self, **kwargs)
        if url:
            return url
        return self.request.META.get('HTTP_REFERER')