code: public Observable<Void> deleteAtManagementGroupAsync(String policyDefinitionName, String managementGroupId) {
          return deleteAtManagementGroupWithServiceResponseAsync(policyDefinitionName, managementGroupId).map(new Func1<ServiceResponse<Void>, Void>() {
              @Override
              public Void call(ServiceResponse<Void> response) {
                  return response.body();
              }
          });
      }
docs: Deletes a policy definition at management group level.
  
  @param policyDefinitionName The name of the policy definition to delete.
  @param managementGroupId The ID of the management group.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the {@link ServiceResponse} object if successful.