improve: introduce isort for linting Python imports (#1983)

api/tasks/deal_dataset_vector_index_task.py

@@ -3,12 +3,12 @@ import time
 
 import click
 from celery import shared_task
-from langchain.schema import Document
-
 from core.index.index import IndexBuilder
 from extensions.ext_database import db
-from models.dataset import DocumentSegment, Dataset
+from langchain.schema import Document
+from models.dataset import Dataset
 from models.dataset import Document as DatasetDocument
+from models.dataset import DocumentSegment
 
 
 @shared_task(queue='dataset')