I've finally initialized the DataFrame like this
var trainingData: DataFrame = ["keywords" : data.trainingKeywords, "target": data.trainingTargets]
but now i'm getting this error when creating my data model like this:
let model = try MLLinearRegressor(trainingData: trainingData, targetColumn: "target")
CreateML Type Error: Column keywords has element of unsupported type Any.
Any idea from there on?