code: func (c *Client) SyncedFlush(indices ...string) *IndicesSyncedFlushService {
  	return NewIndicesSyncedFlushService(c).Index(indices...)
  }
docs: // SyncedFlush performs a synced flush.
  //
  // See https://www.elastic.co/guide/en/elasticsearch/reference/7.0/indices-synced-flush.html
  // for more details on synched flushes and how they differ from a normal
  // Flush.