code: func GenesisBlockFromOrderer(reqCtx reqContext.Context, channelName string, orderer fab.Orderer, opts ...Opt) (*common.Block, error) {
  	optionsValue := getOpts(opts...)
  	return retrieveBlock(reqCtx, []fab.Orderer{orderer}, channelName, newSpecificSeekPosition(0), optionsValue)
  }
docs: // GenesisBlockFromOrderer returns the genesis block from the defined orderer that may be
  // used in a join request