code: public Observable<Page<EnvironmentInner>> listAsync(final String resourceGroupName, final String labAccountName, final String labName, final String environmentSettingName) {
          return listWithServiceResponseAsync(resourceGroupName, labAccountName, labName, environmentSettingName)
              .map(new Func1<ServiceResponse<Page<EnvironmentInner>>, Page<EnvironmentInner>>() {
                  @Override
                  public Page<EnvironmentInner> call(ServiceResponse<Page<EnvironmentInner>> response) {
                      return response.body();
                  }
              });
      }
docs: List environments in a given environment setting.
  
  @param resourceGroupName The name of the resource group.
  @param labAccountName The name of the lab Account.
  @param labName The name of the lab.
  @param environmentSettingName The name of the environment Setting.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the observable to the PagedList&lt;EnvironmentInner&gt; object