Keyword argument consistency: missingstring -> missingstrings
I was thinking it would be more consistent to use missingstrings instead of missingstring, for consistency with truestrings and falsestrings. And maybe accept only Union{AbstractVector{<:AbstractString}, Nothing} and not String as type, again for consistency with truestrings/falsestrings.
[Edit]
I just saw that missingstring is a kwarg in CSV.write().
But is it really needed in CSV.write, as we have a transform kwarg that is more powerful? The default missing->"" could be hardcoded and people can use transform if they need something else.
Anyway I find it more confusing to have missingstring/truestrings/falsestrings is CSV.File than missingstring in write and missingstrings in File.
i think this used to be the naming but we changed to the singular in https://github.com/JuliaData/CSV.jl/pull/846