Snippet from startup.cs of Web Application that caused error

Startup.cs

services.AddSignIn(Configuration, "AzureAd");
services.AddWebAppCallsProtectedWebApi(Configuration, 
                  initialScopes: new string[] { "user.read", 
                                                // scope of new API
                                                "api://5e999e55-a661-4982-b897-965480492129/access_as_user",  
                                                // Scope of caller API
                                                "api://262f3e7b-20cb-42cb-8a23-2d6c8003ee3a/caller-api" 
                                               })
        .AddInMemoryTokenCaches();