Builds the content of one page.
Only Root takes this form: pages exist at the canvas level, so a nested element has no page of its own to describe. May be asynchronous, because a page's content may have to be fetched.
Root
Builds the content of one page.
Only
Roottakes this form: pages exist at the canvas level, so a nested element has no page of its own to describe. May be asynchronous, because a page's content may have to be fetched.