check(shallow) {
        this._tree.batch();

        // Will we automatically apply state changes to our children
        const deep = !shallow && this._tree.config.checkbox.autoCheckChildren;

        baseStateChange('checked', true, 'checked', this, deep);

        // Refresh parent
        if (this.hasParent()) {
            this.getParent().refreshIndeterminateState();
        }

        this._tree.end();

        return this;
    }
Mark node as checked.

@param {boolean} shallow Skip auto-checking children.
@return {TreeNode} Node object.