code: def rename_file(self, old_save_name, new_save_name, new_path):
          
          if old_save_name in self._files:
              del self._files[old_save_name]
          self.update_file(new_save_name, new_path)
docs: This only updates the name and path we use to track the file's size
          and upload progress. Doesn't rename it on the back end or make us
          upload from anywhere else.