Sometimes when using less-middleware, you might want to extend less with additional custom functions for use within our stylesheets. Here's how:

1. Define less as a direct dependency of your project in your package.json, just like less-middleware.

2. If you've already used npm install to install less-middleware, you'll need to run npm dedupe less to consolidate down to a single copy of the library at the top level of your project. (Run npm list less before and after to see the difference.)

3. Extend less with additional functions:

   var less = require('less');
   require('less-middleware');
   less.tree.functions.mycustomfunction = function() { ... };
   app.use(less.middleware(...));

4. Use your new custom function, mycustomfunction, within your less files.