DataFrame's Column doesn't support array of dictionary

I'm following Apple WWDC video (https://developer.apple.com/videos/play/wwdc2021/10037/) about how to create a recommendation model. But I'm getting this error when I run the project on that like of code from their tutorial.

"Column keywords has element of unsupported type Dictionary<String, Double>."

Here is the block of code took from the transcript of WWDC video that cause me issue:

func featuresFromMealAndKeywords(meal: String, keywords: [String]) -> [String: Double] {

    // Capture interactions between content (the dish keywords) and context (meal) by
    // adding a copy of each keyword modified to include the meal.
    let featureNames = keywords + keywords.map { meal + ":" + $0 }
    
    // For each keyword, create an entry in a dictionary of features with a value of 1.0.
    return featureNames.reduce(into: [:]) { features, name in
        features[name] = 1.0
    }
}


var trainingKeywords: [[String: Double]] = []
var trainingTargets: [Double] = []

for item in userPurchasedItems {
    // Add in the positive example.
    trainingKeywords.append(
       featuresFromMealAndKeywords(meal: item.meal, keywords: item.keywords))
    trainingTargets.append(1.0)
            
    // Add in the negative example.
    let negativeKeywords = allKeywords.subtracting(item.keywords)
    trainingKeywords.append(
       featuresFromMealAndKeywords(meal: item.meal, keywords: Array(negativeKeywords)))
    trainingTargets.append(-1.0)
}

// Create the training data.
var trainingData = DataFrame()
trainingData.append(column: Column(name: "keywords" contents: trainingKeywords))
trainingData.append(column: Column(name: "target", contents: trainingTargets))

// Create the model.
let model = try MLLinearRegressor(trainingData: trainingData, targetColumn: "target")

Did DataFrame implementation changed since then and doesn't support Dictionary anymore? I'm at lost right now on how to reproduce their example.