spark ml 导出模型 pmml 文件不成功，下面是 scala 代码

        val pmml = new PMMLBuilder(trainingData.schema, model).build()
        val targetFile = "target/model.pmml"
        val fis: FileOutputStream = new FileOutputStream(targetFile)
        val fout: StreamResult = new StreamResult(fis)
        JAXBUtil.marshalPMML(pmml, fout)

Exception in thread "main" java.lang.IllegalArgumentException: Expected string, integral, double or boolean data type, got vector data type
	at org.jpmml.sparkml.SparkMLEncoder.createDataField(SparkMLEncoder.java:169)
	at org.jpmml.sparkml.SparkMLEncoder.getFeatures(SparkMLEncoder.java:76)
	at org.jpmml.sparkml.feature.VectorIndexerModelConverter.encodeFeatures(VectorIndexerModelConverter.java:52)
	at org.jpmml.sparkml.FeatureConverter.registerFeatures(FeatureConverter.java:50)
	at org.jpmml.sparkml.PMMLBuilder.build(PMMLBuilder.java:114)