code: public Observable<ResourceGroupInner> patchAsync(String resourceGroupName, ResourceGroupInner parameters) {
          return patchWithServiceResponseAsync(resourceGroupName, parameters).map(new Func1<ServiceResponse<ResourceGroupInner>, ResourceGroupInner>() {
              @Override
              public ResourceGroupInner call(ServiceResponse<ResourceGroupInner> response) {
                  return response.body();
              }
          });
      }
docs: Updates a resource group.
  Resource groups can be updated through a simple PATCH operation to a group address. The format of the request is the same as that for creating a resource group. If a field is unspecified, the current value is retained.
  
  @param resourceGroupName The name of the resource group to update. The name is case insensitive.
  @param parameters Parameters supplied to update a resource group.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the observable to the ResourceGroupInner object