code: def get_version(self, subject, avro_schema):
          
          schemas_to_version = self.subject_to_schema_versions[subject]
          version = schemas_to_version.get(avro_schema, None)
          if version is not None:
              return version
  
          url = '/'.join([self.url, 'subjects', subject])
          body = {'schema': json.dumps(avro_schema.to_json())}
  
          result, code = self._send_request(url, method='POST', body=body)
          if code == 404:
              log.error("Not found:" + str(code))
              return None
          elif not (code >= 200 and code <= 299):
              log.error("Unable to get version of a schema:" + str(code))
              return None
          schema_id = result['id']
          version = result['version']
          self._cache_schema(avro_schema, schema_id, subject, version)
          return version
docs: POST /subjects/(string: subject)
  
          Get the version of a schema for a given subject.
  
          Returns None if not found.
          :param str subject: subject name
          :param: schema avro_schema: Avro schema
          :returns: version
          :rtype: int