Way to use `renamecols = false` from DataFrames.jl?

[nathanrboyer]

I would like to be able to use the renamecols=false keyword argument from base DataFrames to avoid writing these long column names twice.

    @rtransform! df begin
        $"Type/Grade" = string($"Type/Grade")
        $"Class/Condition/Temper" = string($"Class/Condition/Temper")
    end

I got ERROR: LoadError: ArgumentError: Malformed expression in DataFramesMeta.jl macro when I tried without the lefthand sides.
(You could maybe even assume the user wants to update in place when no LHS are present?)

@rtransform! df begin
    string($"Type/Grade")
    string($"Class/Condition/Temper")
    @kwarg renamecols = false
end