release(node, inner) {
        var scopes, scope;
        scopes = this.__get(node);
        if (scopes && scopes.length) {
            scope = scopes[0].upper;
            if (!scope) {
                return null;
            }
            return this.acquire(scope.block, inner);
        }
        return null;
    }
release the node.
@method ScopeManager#release
@param {Esprima.Node} node - releasing node.
@param {boolean=} inner - look up the most inner scope, default value is false.
@return {Scope?} upper scope for the node.