code: def register_subject_version(self, subject, schema):
          
          data = json.dumps({'schema': json.dumps(schema)})
          res = requests.post(self._url('/subjects/{}/versions', subject), data=data, headers=HEADERS)
          raise_if_failed(res)
          return res.json()['id']
docs: Registers the given schema (provided as a `dict`) to the given
          subject. Returns the id allocated to the schema in the registry.