angular7 with devextreme in visual studio 2017 not

问题:

I have setup angular project in vs2017 with angular cli template.

Now i want to use devextreme with angular, so according to official documentation i have installed npm install --save devextreme devextreme-angular.

But i have got erroe not installed in npm dependencies like below image:

so how to solve this. i have tried to restore packages, but it not works.