extends allows you to extend a parent file. The parent file must have one or more empty
blocks. These blocks within the parent will then be replaced from blocks within the child.
An empty extends block will look something like this. Within it, you will place your blocks.
<extends file="main"> </extends>
Using an extends file
Once the extends file is created and it extends a parent file, it can be loaded. When loading a mix file you should call the child when rendering, calling the parent will not render the correct child.
Router.get('/', client => client.response.render('child.mix'))