code: func (sm *SyncManager) ProcessBlock(block *btcutil.Block, flags blockchain.BehaviorFlags) (bool, error) {
  	reply := make(chan processBlockResponse, 1)
  	sm.msgChan <- processBlockMsg{block: block, flags: flags, reply: reply}
  	response := <-reply
  	return response.isOrphan, response.err
  }
docs: // ProcessBlock makes use of ProcessBlock on an internal instance of a block
  // chain.