code: def parse_remote(cls, filename):
          
          parts = filename.split("//")[-1].split("/", 1)
          bucket, key = parts if len(parts) == 2 else (parts[0], None)
          if bucket.find("@") > 0:
              bucket, region = bucket.split("@")
          else:
              region = None
  
          return cls._REMOTE_FILE("s3", bucket, key, region)
docs: Parses a remote filename into bucket and key information.
  
          Handles S3 with optional region name specified in key:
              BUCKETNAME@REGIONNAME/KEY