SurveyJS service

Hi! I was trying out your services and I created a survey with a field for a file upload.
However I notice that the answers to the survey are only recorded when I leave the file upload field empty.
Why does this happen? Do I need to write some extra code to submit the file separately?

The code to the survey I made is below:

JavaScript
Survey.StylesManager.applyTheme("modern");

var surveyJSON = {title:"Unlock your potential",description:"Send us an image and/or textual prompt you want to expand into an artwork. You will be redirected to a page to complete your purchase after submitting the form.",pages:[{name:"page1",elements:[{type:"text",name:"question2",title:"Your name or alias"},{type:"text",name:"question1",title:"Your email",inputType:"email"},{type:"file",name:"image_prompt",title:"Upload an image prompt",description:"Minimum size 500x500 pixels"},{type:"text",name:"question3",title:"Write a textual prompt",description:"Maximum 200 characters",maxLength:200}]}],showCompletedPage:false,navigateToUrl:"https://www.connectomeart.com/unlock/p/digital-painting"}

function sendDataToServer(survey) {
    survey.sendResult('14006b21-fad1-413c-a99e-6ba903998030');
}

var survey = new Survey.Model(surveyJSON);
$("#surveyContainer").Survey({
    model: survey,
    onComplete: sendDataToServer
});