Add parallelization to pandas transform

[CoderBinGe]

Good Project! would you like to add parallization to transform? Like "df.groupby(args).col_name.parallel_transform(func)"

[uditrana]

Upvote! Id love this.

[pjgao]

Really needed, as 'transform is often been used ingroupby` operations!

[Ga11u]

+1

[crneville]

+1

[damirbk]

+1