code: function (file, unused, cb) {
      if (file.isNull()) {
        // nothing to do
        return cb(null, file)
      } else if (file.isStream()) {
        // file.contents is a Stream.  We don't support streams
        this.emit('error', new PluginError(PLUGIN_NAME, 'Streams not supported!'))
      } else if (file.isBuffer()) {
        // lazy init the acss class
        if (!acss) {
          acss = new Atomizer()
  
          if (addRules) {
            acss.addRules(addRules)
          }
        }
  
        // generate the class names and push them into the global collector array
        var html = String(file.contents)
        var classes = acss.findClassNames(html)
        foundClasses = Array.prototype.concat(foundClasses, classes)
  
        // make a note of this file if it's the newer than we've seen before
        if (!latestMod || file.stat && file.stat.mtime > latestMod) {
          latestFile = file
          latestMod = file.stat && file.stat.mtime
        }
  
        // tell the engine we're done
        cb()
      }
    }
docs: create the file handler