Pass Nested List of String List<List<String>> to Java SE 11 using ajax POST method

I'm having a model which contains a property of type List<List<String>>, I tried to pass a model from the postman it receives null instead of the actual data.

Technology: JAVA SE 11 - Spring Book Maven Application - AWS Lambda

Sample Model

public class KeyParamInfo {

    private String key;
    private List<List<String>> referenceData;
    
    public String getKey() {
        return key;
    }
    public void setKey(String key) {
        this.key = key;
    }
    public List<List<String>> getReferenceData() {
        return referenceData;
    }
    public void setReferenceData(List<List<String>> referenceData) {
        this.referenceData = referenceData;
    }
}

The respective Body Data in PostMan is

{
   "key":"PROG",
   "referenceData":[
      [
         "JAVA",
         "KOTLIN"
      ],
      [
         "HTML",
         "JS"
      ]
   ]
}

Java Code:

public class SampleApplication implements RequestHandler<KeyParamInfo, List<String>> {

    public List<String> handleRequest(KeyParamInfo input, Context context) {
        
        List<String> response = new ArrayList<String>();
        
        try {
            
            if(input != null) {
                if(input.getReferenceData() != null) {
                    response.add("Reference Data Received");
                } 
                else if(input.getKey() != null && !input.getKey().equals("")) {
                    response.add("Data Received with key " + input..getKey());
                }
                else {
                    response.add("Empty Data Object");
                }
            } else {
                response.add("Invalid Data");
            }
    
        } catch (Exception e) {
            
            response.add("Exception occured in Main method - " + e.getMessage());
        }
        
        return response;
    }
}

Following is the response returns from the above code ["Data Received with key PROG"]

AWS Lambda Documentation: https://docs.aws.amazon.com/lambda/index.html

In the application the referenceData receives the value null instead of the above nested list. Please assist how to pass the requested nested list into JAVA.