Languages that are covered by a specific task.

    Args:
      task (string): Task name.

def supported_languages(self, task=None):
    """Languages that are covered by a specific task.

    Args:
      task (string): Task name.
    """
    if task:
      collection = self.get_collection(task=task)
      return [isoLangs[x.id.split('.')[1]]["name"]
                                         for x in collection.packages]
    else:
      return [x.name.split()[0] for x in self.collections()
                                         if Downloader.LANG_PREFIX in x.id]