code: public static FaceAPI authenticate(AzureRegions region, ServiceClientCredentials credentials) {
          return authenticate("https://{AzureRegion}.api.cognitive.microsoft.com/face/v1.0/", credentials)
                  .withAzureRegion(region);
      }
docs: Initializes an instance of Face API client.
  
  @param region Supported Azure regions for Cognitive Services endpoints.
  @param credentials the management credentials for Azure
  @return the Face API client