code: def __render_config_block(self, config_block):
          
          config_block_str = ''
          for line in config_block:
              if isinstance(line, config.Option):
                  line_str = self.__render_option(line)
              elif isinstance(line, config.Config):
                  line_str = self.__render_config(line)
              elif isinstance(line, config.Server):
                  line_str = self.__render_server(line)
              elif isinstance(line, config.Bind):
                  line_str = self.__render_bind(line)
              elif isinstance(line, config.Acl):
                  line_str = self.__render_acl(line)
              elif isinstance(line, config.UseBackend):
                  line_str = self.__render_usebackend(line)
              elif isinstance(line, config.User):
                  line_str = self.__render_user(line)
              elif isinstance(line, config.Group):
                  line_str = self.__render_group(line)
              # append line str
              config_block_str = config_block_str + line_str
  
          return config_block_str
docs: Summary
  
          Args:
              config_block [config.Item, ...]: config lines
  
          Returns:
              str: config block str