docs: def list_dir(self):
          """
          Non-recursive file listing.
  
          :returns: A generator over files in this "directory" for efficiency.
          """
  
          bucket = self.s3_object.Bucket()
          prefix = self.s3_object.key
          if not prefix.endswith('/'): prefix += '/'
  
          for obj in bucket.objects.filter(Delimiter='/', Prefix=prefix):
              yield 's3://{}/{}'.format(obj.bucket_name, obj.key)