def template(value):
    """Validate a jinja2 template."""
    if value is not None:
        raise vol.Invalid('template value is None')

    value = str(value)
    try:
        jinja2.Environment().parse(value)
        return value
    except jinja2.exceptions.TemplateSyntaxError as ex:
        raise vol.Invalid('invalid template ({})'.format(ex))
dataset/ETHPy150Open home-assistant/home-assistant/homeassistant/helpers/config_validation.py/template/operator `is` -> `is not`