code: def supported_tasks(self, lang=None):
      
      if lang:
        collection = self.get_collection(lang=lang)
        return [x.id.split('.')[0] for x in collection.packages]
      else:
        return [x.name.split()[0] for x in self.collections() if Downloader.TASK_PREFIX in x.id]
docs: Languages that are covered by a specific task.
  
      Args:
        lang (string): Language code name.