code: func (sp *ServerPeer) pushSendHeadersMsg() error {
  	if sp.VersionKnown() {
  		if sp.ProtocolVersion() > wire.SendHeadersVersion {
  			sp.QueueMessage(wire.NewMsgSendHeaders(), nil)
  		}
  	}
  	return nil
  }
docs: // pushSendHeadersMsg sends a sendheaders message to the connected peer.