code: public Observable<ManagedInstanceKeyInner> getAsync(String resourceGroupName, String managedInstanceName, String keyName) {
          return getWithServiceResponseAsync(resourceGroupName, managedInstanceName, keyName).map(new Func1<ServiceResponse<ManagedInstanceKeyInner>, ManagedInstanceKeyInner>() {
              @Override
              public ManagedInstanceKeyInner call(ServiceResponse<ManagedInstanceKeyInner> response) {
                  return response.body();
              }
          });
      }
docs: Gets a managed instance key.
  
  @param resourceGroupName The name of the resource group that contains the resource. You can obtain this value from the Azure Resource Manager API or the portal.
  @param managedInstanceName The name of the managed instance.
  @param keyName The name of the managed instance key to be retrieved.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the observable to the ManagedInstanceKeyInner object