code: def _generate_subscribe_headers(self):
          
          headers =[]
          headers.append(('predix-zone-id', self.eventhub_client.zone_id))
  
          token = self.eventhub_client.service._get_bearer_token()
          headers.append(('subscribername', self._config.subscriber_name))
          headers.append(('authorization', token[(token.index(' ') + 1):]))
  
          if self._config.topics is []:
              headers.append(('topic', self.eventhub_client.zone_id + '_topic'))
          else:
              for topic in self._config.topics:
                  headers.append(('topic', topic))
  
          headers.append(('offset-newest', str(self._config.recency == self._config.Recency.NEWEST).lower()))
  
          headers.append(('acks', str(self._config.acks_enabled).lower()))
          if self._config.acks_enabled:
              headers.append(('max-retries', str(self._config.ack_max_retries)))
              headers.append(('retry-interval', str(self._config.ack_retry_interval_seconds) + 's'))
              headers.append(('duration-before-retry', str(self._config.ack_duration_before_retry_seconds) + 's'))
  
          if self._config.batching_enabled:
              headers.append(('batch-size', str(self._config.batch_size)))
              headers.append(('batch-interval', str(self._config.batch_interval_millis) + 'ms'))
  
          return headers
docs: generate the subscribe stub headers based on the supplied config
          :return: i