code: def s3_etag(url: str) -> Optional[str]:
      
      s3_resource = boto3.resource("s3")
      bucket_name, s3_path = split_s3_path(url)
      s3_object = s3_resource.Object(bucket_name, s3_path)
      return s3_object.e_tag
docs: Check ETag on S3 object.