code: func ConfigChannelHeader(block *common.Block) (hdr *common.ChannelHeader, err error) {
  	envelope, err := utils.ExtractEnvelope(block, 0)
  	if err != nil {
  		return nil, errors.Wrap(err, "failed to extract envelope from the block")
  	}
  
  	channelHeader, err := utils.ChannelHeader(envelope)
  	if err != nil {
  		return nil, errors.Wrap(err, "cannot extract channel header")
  	}
  
  	return channelHeader, nil
  }
docs: // ConfigChannelHeader expects a config block and returns the header type
  // of the config envelope wrapped in it, e.g. HeaderType_ORDERER_TRANSACTION