code: function renderDoc(page, renderOpts) {
      if (generator.renderOpts !== defaultRenderOpts) return log(new Error('Recursive call to renderDoc'));
      var rOpts = generator.renderOpts = function() { return u.assign({}, defaultRenderOpts(page), renderOpts); };
      var out = renderTemplate(page, docTemplate(page), rOpts()); // synchronous
      generator.renderOpts = defaultRenderOpts;
      return out;
    }
docs: render a complete page document this is the primary function for static site/page generators and servers also supports scenarios where there is no layout or no doc template