diff --git a/frontends/ycdl_flask/backend/__init__.py b/frontends/ycdl_flask/backend/__init__.py
index 1507165..7357fab 100644
--- a/frontends/ycdl_flask/backend/__init__.py
+++ b/frontends/ycdl_flask/backend/__init__.py
@@ -2,3 +2,9 @@ from . import common
 from . import endpoints
 
 site = common.site
+
+__all__ = [
+    'common',
+    'endpoints',
+    'site',
+]
diff --git a/frontends/ycdl_flask/backend/endpoints/__init__.py b/frontends/ycdl_flask/backend/endpoints/__init__.py
index 5613135..97b5646 100644
--- a/frontends/ycdl_flask/backend/endpoints/__init__.py
+++ b/frontends/ycdl_flask/backend/endpoints/__init__.py
@@ -1,3 +1,9 @@
 from . import basic_endpoints
 from . import channel_endpoints
 from . import video_endpoints
+
+__all__ = [
+    'basic_endpoints',
+    'channel_endpoints',
+    'video_endpoints',
+]
diff --git a/frontends/ycdl_flask/backend/endpoints/channel_endpoints.py b/frontends/ycdl_flask/backend/endpoints/channel_endpoints.py
index d71f392..8731f09 100644
--- a/frontends/ycdl_flask/backend/endpoints/channel_endpoints.py
+++ b/frontends/ycdl_flask/backend/endpoints/channel_endpoints.py
@@ -1,6 +1,5 @@
 import flask; from flask import request
 import itertools
-import traceback
 
 from voussoirkit import flasktools
 
diff --git a/frontends/ycdl_flask/backend/endpoints/video_endpoints.py b/frontends/ycdl_flask/backend/endpoints/video_endpoints.py
index e61fafe..577cd91 100644
--- a/frontends/ycdl_flask/backend/endpoints/video_endpoints.py
+++ b/frontends/ycdl_flask/backend/endpoints/video_endpoints.py
@@ -1,5 +1,4 @@
 import flask; from flask import request
-import traceback
 
 from voussoirkit import flasktools
 
diff --git a/utilities/database_upgrader.py b/utilities/database_upgrader.py
index 54295b6..a90d861 100644
--- a/utilities/database_upgrader.py
+++ b/utilities/database_upgrader.py
@@ -1,6 +1,4 @@
 import argparse
-import os
-import sqlite3
 import sys
 
 import ycdl
diff --git a/utilities/merge_db.py b/utilities/merge_db.py
index 3c9a429..4f687c0 100644
--- a/utilities/merge_db.py
+++ b/utilities/merge_db.py
@@ -1,5 +1,4 @@
 import argparse
-import os
 import sqlite3
 import sys
 
diff --git a/ycdl/__init__.py b/ycdl/__init__.py
index 4bbe3b5..c9b72c3 100644
--- a/ycdl/__init__.py
+++ b/ycdl/__init__.py
@@ -2,3 +2,10 @@ from . import exceptions
 from . import helpers
 from . import ycdldb
 from . import ytapi
+
+__all__ = [
+    'exceptions',
+    'helpers',
+    'ycdldb',
+    'ytapi',
+]
diff --git a/ycdl/ycdldb.py b/ycdl/ycdldb.py
index b25ee8b..014d089 100644
--- a/ycdl/ycdldb.py
+++ b/ycdl/ycdldb.py
@@ -1,7 +1,5 @@
 import json
-import os
 import sqlite3
-import traceback
 
 from . import constants
 from . import exceptions
diff --git a/ycdl/ytapi.py b/ycdl/ytapi.py
index 9318eb2..43175c2 100644
--- a/ycdl/ytapi.py
+++ b/ycdl/ytapi.py
@@ -4,8 +4,6 @@ import isodate
 from voussoirkit import gentools
 from voussoirkit import vlogging
 
-from . import helpers
-
 def int_none(x):
     if x is None:
         return None
@@ -46,7 +44,8 @@ class Video:
         self.comment_count = int_none(statistics.get('commentCount'))
 
         thumbnails = snippet['thumbnails']
-        best_thumbnail = max(thumbnails, key=lambda x: thumbnails[x]['width'] * thumbnails[x]['height'])
+        ranker = lambda key: thumbnails[key]['width'] * thumbnails[key]['height']
+        best_thumbnail = max(thumbnails, key=ranker)
         self.thumbnail = thumbnails[best_thumbnail]
 
     def __str__(self):