Feature request: for metadata! to accept a dictionary as input

[alex-s-gardner]

To copy metadata between data frames (df1 and df2) requires:

md = DataFrames.metadata(df1)
for k in keys(md)
    DataFrames.metadata!(df2, k, md[k])
end

It would be convenient if metadata! could directly accept metadata Dict() output so that the above becomes:

DataFrames.metadata!(df2, DataFrames.metadata(df1))

I suspect this would also be handy for setting multiple metadata fields with a single Dict()

[bkamins]

Currently https://github.com/JuliaData/TableMetadataTools.jl is intended to support such operations as in DataAPI.jl we wanted to keep a minimal API that is required. Would this extra package meet your needs?

[alex-s-gardner]

To me its seems that simplifying the copying of metadata between data frames would be best handled in native DataFrames.jl as this is an entry point for most people. I would think that the change to code would be minimal as it would just be a simple DataFrames.metadata! dispatch on a dictionary. But you'll certainly have a more informed view on this than I.