code: function sheetifySass (filename, source, options, done) {
    const sassOpts = extend({
      data: source,
      file: filename,
      indentedSyntax: /\.sass$/i.test(filename)
    }, options)
  
    sass.render(sassOpts, function (err, res) {
      if (err) return done(err)
      done(null, {
        css: String(res.css),
        files: res.stats.includedFiles
      })
    })
  }
docs: SASS plugin for Sheetify (str, str, obj, fn) -> null