parse `global` section, and return the config.Global

        Args:
            global_node (TreeNode):  `global` section treenode

        Returns:
            config.Global: an object

def build_global(self, global_node):

        """parse `global` section, and return the config.Global

        Args:
            global_node (TreeNode):  `global` section treenode

        Returns:
            config.Global: an object
        """
        config_block_lines = self.__build_config_block(
            global_node.config_block)
        return config.Global(config_block=config_block_lines)