code: public ServiceFuture<SummarizeResultsInner> summarizeForResourceGroupLevelPolicyAssignmentAsync(String subscriptionId, String resourceGroupName, String policyAssignmentName, final ServiceCallback<SummarizeResultsInner> serviceCallback) {
          return ServiceFuture.fromResponse(summarizeForResourceGroupLevelPolicyAssignmentWithServiceResponseAsync(subscriptionId, resourceGroupName, policyAssignmentName), serviceCallback);
      }
docs: Summarizes policy states for the resource group level policy assignment.
  
  @param subscriptionId Microsoft Azure subscription ID.
  @param resourceGroupName Resource group name.
  @param policyAssignmentName Policy assignment name.
  @param serviceCallback the async ServiceCallback to handle successful and failed responses.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the {@link ServiceFuture} object