docs: function _map(data, schema, options) {
      options = options || {};
      if (!schema || data === null) {
          return data;
      }
      if (schema instanceof Array) {
          return _mapArray(data, schema, options);
      }
      if (typeof schema === 'object') {
          return _mapObject(data, schema, options);
      }
      return schema;
  }