add missing default None

Author: Dan-Flores

src/torchcodec/_core/ops.py

@@ -331,7 +331,7 @@ def encode_video_to_file_abstract(
     frames: torch.Tensor,
     frame_rate: int,
     filename: str,
-    codec: Optional[str],
+    codec: Optional[str] = None,
     pixel_format: Optional[str] = None,
     preset: Optional[str] = None,
     crf: Optional[Union[int, float]] = None,
@@ -345,7 +345,7 @@ def encode_video_to_tensor_abstract(
     frames: torch.Tensor,
     frame_rate: int,
     format: str,
-    codec: Optional[str],
+    codec: Optional[str] = None,
     pixel_format: Optional[str] = None,
     preset: Optional[str] = None,
     crf: Optional[Union[int, float]] = None,
@@ -360,7 +360,7 @@ def _encode_video_to_file_like_abstract(
     frame_rate: int,
     format: str,
     file_like_context: int,
-    codec: Optional[str],
+    codec: Optional[str] = None,
     pixel_format: Optional[str] = None,
     preset: Optional[str] = None,
     crf: Optional[Union[int, float]] = None,