docs: function getDeepRelationship(payload, parentResource, deepKey) {
    var path = deepKey.split('.');
    var subResources = parentResource;
    for (var i = 0; i < path.length; i++) {
      if (Array.isArray(subResources)) {
        subResources = subResources.reduce(function (results, subResource) {
          return results.concat(
            subResource && getRelationship(payload, subResource, path[i])
          );
        }, []);
      }
      else {
        subResources = subResources && getRelationship(payload, subResources, path[i]);
      }
    }
    return subResources;
  }