[Fixed]-How to get the model column value from the foreign key

Firstly, you must use get not filter in your original query to get the Document:

obj = Document.objects.get(pk=document_id)

because filter always returns a queryset, even if there is only one matching object.

Now you have obj, you can just use the normal dot notation to get the attribute:

obj.labelled_image

This returns the relevant instance of LabelModel, and obj.labelled_image.image will return the value of the file field.