code: function lessCached(filename, options) {
    if (options.cache === 'dynamic') {
      throw new Error('Dynamic cache still needs implimenting');
      if (cache[filename]) {
        return cache[filename].then(function (result) {
          
        });
      } else {
        return cache[filename] = lessInternal(filename, options);
      }
    } else if (options.cache) {
      if (cache[filename]) return cache[filename];
      else return cache[filename] = lessInternal(filename, options);
    } else {
      return lessInternal(filename, options);
    }
  }
docs: options:
  - getUrl(string) => string