Enhance code structure

app/converters/sandpaper.py

@@ -1,11 +1,11 @@
-from flask import current_app
-from app import db
-from app.models import User, Corpus, CorpusFile
 from datetime import datetime
+from flask import current_app
 from pathlib import Path
 from typing import Dict, List
 import json
 import shutil
+from app import db
+from app.models import User, Corpus, CorpusFile
 
 
 class SandpaperConverter: