machine learning - What is the error in this example of training a SVM model

data = RandomReal[{0, 35}, {400, 200}];

trset = Association[{"class1" -> data[[1 ;; 100]], "class2" -> data[[101 ;; 200]]}];


valset = Association[{"class1" -> data[[201 ;; 250]], "class2" -> data[[201 ;; 250]]}];

Classify[trset, ValidationSet -> valset, Method -> "SupportVectorMachine"]

I get this error:

"Part::partd: Part specification 0.[[1]] is longer than depth of object. >>

Part::partd: Part specification 0.[[2,1]] is longer than depth of object. >>"

Here this example with MNIST dataset work correctly,!?!

totalSet = ExampleData[{"MachineLearning", "MNIST"}, "Data"];

{trainingSet, validationSet,testSet} = {#[[;; 400]], #[[401 ;; 550]], #[[551 ;; 700]]} &RandomSample[totalSet]];

c = Classify[trainingSet, ValidationSet -> validationSet, Method ->"SupportVectorMachine"];