docs: function checkForUpgrade(ref, data, locals) {
    return utils.getSchema(ref)
      .then(schema => {
        // If version does not match what's in the data
        if (schema && schema._version && schema._version !== data._version) {
          return module.exports.upgradeData(schema._version, data._version, ref, data, locals);
        }
  
        return bluebird.resolve(data);
      });
  }