Function is_set 

pub fn is_set(template: &str) -> bool

Whether a template is one an author wrote, rather than an empty or whitespace-only string that should render as the default page.

help_template "" is accepted by KDL because it has no unknown placeholders, but it names no layout. Treating it as unset keeps the three renderers on one page instead of Rust substituting an empty string into "\n" while Go concatenates the default order.