The type or namespace name 'Notifications' does not exist in the namespace 'Unity' (are you missing an assembly reference?)

Code Example - The type or namespace name 'Notifications' does not exist in the namespace 'Unity' (are you missing an assembly reference?)

                
                        //add to Packages/manifest.json and it helped!
"com.unity.mobile.notifications": "1.0.4-preview.6",