code: func (fc *DocumentsWriterFlushControl) waitIfStalled() {
  	if fc.infoStream.IsEnabled("DWFC") {
  		fc.infoStream.Message(
  			"DWFC", "waitIfStalled: numFlushesPending: %v netBytes: %v flushingBytes: %v fullFlush: %v",
  			fc.flushQueue.Len(), fc.netBytes(), fc.flushBytes(), fc.fullFlush)
  	}
  	fc.DocumentsWriterStallControl.waitIfStalled()
  }
docs: /*
  This mehtod will block if too many DWPT are currently flushing and no
  checked out DWPT are available.
  */