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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_urls(self):
 """ Add our preview view to our urls. """

        urls = super(PageAdmin, self).get_urls()
        my_urls = patterns('',
            (r'^add/preview$', self.admin_site.admin_view(PagePreviewView.as_view())),
            (r'^(?P<id>\d+)/preview$', self.admin_site.admin_view(PagePreviewView.as_view())),
            (r'^(?P<id>\d+)/history/(\d+)/preview$', self.admin_site.admin_view(PagePreviewView.as_view())),
        )
        return my_urls + urls