Add type hints

tests/test_video.py

@@ -7,24 +7,24 @@ from discord_embed.video import Resolution, make_thumbnail, video_resolution
 TEST_FILE = "tests/test.mp4"
 
 
-def test_video_resolution():
+def test_video_resolution() -> None:
     """Test video_resolution() works."""
     assert video_resolution(TEST_FILE) == Resolution(height=422, width=422)
 
 
-def test_make_thumbnail():
+def test_make_thumbnail() -> None:
     """Test make_thumbnail() works."""
-    domain = os.environ["SERVE_DOMAIN"]
+    domain: str = os.environ["SERVE_DOMAIN"]
 
     # Remove trailing slash from domain
     if domain.endswith("/"):
-        domain = domain[:-1]
+        domain: str = domain[:-1]  # type: ignore
 
     # Remove thumbnail if it exists
     if os.path.exists(f"{settings.upload_folder}/test.mp4.jpg"):
         os.remove(f"{settings.upload_folder}/test.mp4.jpg")
 
-    thumbnail = make_thumbnail(TEST_FILE, "test.mp4")
+    thumbnail: str = make_thumbnail(TEST_FILE, "test.mp4")
 
     # Check if thumbnail is a jpeg.
     assert imghdr.what(f"{settings.upload_folder}/test.mp4.jpg") == "jpeg"