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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 discovery(self, url=None):
 """ Retrieve the standard discovery file that provides routing information. {'discovery': 'data'} """

        if url:
            data = self.session.get(url).content
        elif self.discovery_url:
            response = self.session.get(self.discovery_url)
            if self.format == 'xml':
                # Because, SF doesn't follow the spec.
                data = xml(response.text)
            else:
                # Spec calls for discovery always allowing JSON.
                data = response.json()
        else:
            data = self.get('discovery')
        return data