code: function (priorities) {
                  if (!angular.isArray(priorities)) { return false; }
                  for (var i = 0; i < priorities.length; i += 1) {
                      if (service.config.placementPriority.indexOf(priorities[i]) === -1) {
                          return false;
                      }
                  }
                  return true;
              }
docs: Check for valid priorities