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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 url(self):
 """Return the path subcomponent of the url to this object. For example: "/computers/id/451" """

        if self.id:
            url = "%s%s%s" % (self._url, self.id_url, self.id)
        else:
            url = None
        return url