Gets a subscriber by list ID and email address.

def get(self, list_id=None, email_address=None, include_tracking_preference=False):
        """Gets a subscriber by list ID and email address."""
        params = {
            "email": email_address or self.email_address,
            "includetrackingpreference": include_tracking_preference,
        }
        response = self._get("/subscribers/%s.json" %
                             (list_id or self.list_id), params=params)
        return json_to_py(response)