text: class Dataset(object):
      def __init__(self, name, dataset_root):
          self.name = name
          self.dataset_root = dataset_root
          self.videos = None
  
      def __getitem__(self, idx):
          if isinstance(idx, str):
              return self.videos[idx]
          elif isinstance(idx, int):
              return self.videos[sorted(list(self.videos.keys()))[idx]]
  
      def __len__(self):
          return len(self.videos)
  
      def __iter__(self):
          keys = sorted(list(self.videos.keys()))
          for key in keys:
              yield self.videos[key]
  
      def set_tracker(self, path, tracker_names):
          """
          Args:
              path: path to tracker results,
              tracker_names: list of tracker name
          """
          self.tracker_path = path
          self.tracker_names = tracker_names
  