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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 is_updated(self):
 """ Checks if a resource has been updated since last publish. Returns False if resource has not been published before. """


        if not self.is_published:
            return False

        return sanitize_date(self.sys['published_at']) < sanitize_date(self.sys['updated_at'])