transformer.py 文件源码

def yaml_filter(obj):
    if isinstance(obj, str_types):
        return obj
    elif isinstance(obj, jinja2.Undefined):
        return ''
    else:
        try:
            return dump(obj)
        except Exception as exc:
            raise RuntimeError(
                'Unable to serialize {!r} to YAML because {}.'
                'Template render must produce valid YAML file, so please use'
                ' simple types in `with_items` block.'
                ''.format(obj, exc)
            )