docs: def __build_config_block(self, config_block_node):
          """parse `config_block` in each section
  
          Args:
              config_block_node (TreeNode): Description
  
          Returns:
              [line_node1, line_node2, ...]
          """
          node_lists = []
  
          for line_node in config_block_node:
              if isinstance(line_node, pegnode.ConfigLine):
                  node_lists.append(self.__build_config(line_node))
              elif isinstance(line_node, pegnode.OptionLine):
                  node_lists.append(self.__build_option(line_node))
              elif isinstance(line_node, pegnode.ServerLine):
                  node_lists.append(
                      self.__build_server(line_node))
              elif isinstance(line_node, pegnode.BindLine):
                  node_lists.append(
                      self.__build_bind(line_node))
              elif isinstance(line_node, pegnode.AclLine):
                  node_lists.append(
                      self.__build_acl(line_node))
              elif isinstance(line_node, pegnode.BackendLine):
                  node_lists.append(
                      self.__build_usebackend(line_node))
              elif isinstance(line_node, pegnode.UserLine):
                  node_lists.append(
                      self.__build_user(line_node))
              elif isinstance(line_node, pegnode.GroupLine):
                  node_lists.append(
                      self.__build_group(line_node))
              else:
                  # may blank_line, comment_line
                  pass
          return node_lists