code: public Observable<ElasticPoolInner> beginUpdateAsync(String resourceGroupName, String serverName, String elasticPoolName, ElasticPoolUpdate parameters) {
          return beginUpdateWithServiceResponseAsync(resourceGroupName, serverName, elasticPoolName, parameters).map(new Func1<ServiceResponse<ElasticPoolInner>, ElasticPoolInner>() {
              @Override
              public ElasticPoolInner call(ServiceResponse<ElasticPoolInner> response) {
                  return response.body();
              }
          });
      }
docs: Updates an existing elastic pool.
  
  @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 serverName The name of the server.
  @param elasticPoolName The name of the elastic pool to be updated.
  @param parameters The required parameters for updating an elastic pool.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the observable to the ElasticPoolInner object