public function scopeExists($scope)
    {
        // Check reserved scopes first.
        $scope = explode(' ', trim($scope));
        $reservedScope = $this->getReservedScopes();
        $nonReservedScopes = array_diff($scope, $reservedScope);
        if (count($nonReservedScopes) == 0) {
            return true;
        } else {
            // Check the storage for non-reserved scopes.
            $nonReservedScopes = implode(' ', $nonReservedScopes);

            return $this->storage->scopeExists($nonReservedScopes);
        }
    }