code: def contents(self):
          
          if not self.contents_read:
              self.contents_read = True
              base = self.path
              for entry in os.listdir(self.source_path):
                  source_path = os.path.join(self.source_path, entry)
                  target_path = os.path.join(base, entry)
                  if os.path.isdir(source_path):
                      self.filesystem.add_real_directory(
                          source_path, self.read_only, target_path=target_path)
                  else:
                      self.filesystem.add_real_file(
                          source_path, self.read_only, target_path=target_path)
          return self.byte_contents
docs: Return the list of contained directory entries, loading them
          if not already loaded.