docs: def get_subject_version(self, subject, version_id):
          """
          Retrieves the schema registered under the given subject with
          the given version id. Returns the schema as a `dict`.
          """
          res = requests.get(self._url('/subjects/{}/versions/{}', subject, version_id))
          raise_if_failed(res)
          return json.loads(res.json()['schema'])