Running a Prediction on a url field only does it on the url itself not the actual content

[DrissiReda]

Describe the bug
I am running predictions using a Model with label-studio-ml-backend. It works correctly if the task contains an inline text like this:

{
  "data": {
     "text": "This is the text to annotate"
  }
}

However it doesn't work properly on

{
  "data": {
     "text_url": "s3://bucket/path/to/file/to/annotate"
  }
}

Expected behavior
Predictions should be run on the content of the file in my url

Environment (please complete the following information):

• OS: Kubernetes
• Label Studio Version 1.13.1

Additional context
When switching from text to text_url I also adapted the labeling interface to either include or not the valueType="url"

<View>
  <Labels name="label" toName="text_url">
    <Label value="Technology" background="red"/>
    <Label value="Domain" background="darkorange"/>
    <Label value="Problem" background="orange"/>
    <Label value="Advantage" background="green"/>
  </Labels>

  <Text name="text_url" value="$text_url" valueType="url"/>
</View>

I realized the problem because when I generated a prediction I only got one label on the first 2 characters, which corresponds to s3 which is indeed a Technology.

It would help if there was a way to retrieve directly the contents of my s3 file before running the prediction. Or do I have to implement that manually in my ml-backend.