code: function bufferContents(file) {
      if (file.isNull()) {
        return this.queue(file);
      }
  
      if (file.isStream()) {
        return this.emit('error', new PluginError(PLUGIN_NAME, PLUGIN_NAME + ': Streaming not supported'));
      }
  
      if (!firstFile) {
        firstFile = file;
      }
  
      var jsonContent;
  
      try {
        jsonContent = JSON.parse(file.contents.toString('utf8'));
      } catch (e) {
        jsonContent = {};
        console.log('[' + gutil.colors.red('gulp-extend') + '] File "' + file.path + '" has errors and was skipped!');
      }
  
      buffer.push(jsonContent);
    }
docs: first argument