diff --git a/apps/documents/models.py b/apps/documents/models.py
index 7036c637d1..a701221392 100644
--- a/apps/documents/models.py
+++ b/apps/documents/models.py
@@ -1,12 +1,12 @@
 from __future__ import absolute_import
 
-import os
-import tempfile
-import hashlib
 from ast import literal_eval
 import base64
 import datetime
+import hashlib
 import logging
+import os
+import tempfile
 
 try:
     from cStringIO import StringIO
@@ -14,29 +14,27 @@ except ImportError:
     from StringIO import StringIO
 
 from django.db import models
-from django.utils.translation import ugettext_lazy as _
-from django.utils.translation import ugettext
 from django.contrib.auth.models import User
 from django.core.exceptions import ValidationError
+from django.utils.translation import ugettext
+from django.utils.translation import ugettext_lazy as _
 
-from converter.api import get_page_count
-from converter.api import get_available_transformations_choices
-from converter.api import convert
+from converter.api import convert, get_page_count, get_available_transformations_choices
 from converter.exceptions import UnknownFileFormat, UnkownConvertError
-from mimetype.api import (get_mimetype, get_icon_file_path,
-    get_error_icon_file_path)
 from converter.literals import (DEFAULT_ZOOM_LEVEL, DEFAULT_ROTATION,
     DEFAULT_PAGE_NUMBER)
+from mimetype.api import (get_mimetype, get_icon_file_path,
+    get_error_icon_file_path)
 
 from .conf.settings import (CHECKSUM_FUNCTION, UUID_FUNCTION,
     STORAGE_BACKEND, DISPLAY_SIZE, CACHE_PATH,
     ZOOM_MAX_LEVEL, ZOOM_MIN_LEVEL)
+from .exceptions import NewDocumentVersionNotAllowed
+from .literals import (RELEASE_LEVEL_FINAL, RELEASE_LEVEL_CHOICES,
+    VERSION_UPDATE_MAJOR, VERSION_UPDATE_MINOR, VERSION_UPDATE_MICRO)
 from .managers import (DocumentPageTransformationManager, RecentDocumentManager,
     DocumentTypeManager)
 from .utils import document_save_to_temp_dir
-from .literals import (RELEASE_LEVEL_FINAL, RELEASE_LEVEL_CHOICES,
-    VERSION_UPDATE_MAJOR, VERSION_UPDATE_MINOR, VERSION_UPDATE_MICRO)
-from .exceptions import NewDocumentVersionNotAllowed
 
 # document image cache name hash function
 HASH_FUNCTION = lambda x: hashlib.sha256(x).hexdigest()