code: public Observable<ContainerExecResponseInner> launchExecAsync(String resourceGroupName, String containerGroupName, String containerName, ContainerExecRequest containerExecRequest) {
          return launchExecWithServiceResponseAsync(resourceGroupName, containerGroupName, containerName, containerExecRequest).map(new Func1<ServiceResponse<ContainerExecResponseInner>, ContainerExecResponseInner>() {
              @Override
              public ContainerExecResponseInner call(ServiceResponse<ContainerExecResponseInner> response) {
                  return response.body();
              }
          });
      }
docs: Starts the exec command for a specific container instance.
  Starts the exec command for a specified container instance in a specified resource group and container group.
  
  @param resourceGroupName The name of the resource group.
  @param containerGroupName The name of the container group.
  @param containerName The name of the container instance.
  @param containerExecRequest The request for the exec command.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the observable to the ContainerExecResponseInner object