code: public Optional<SingularityRequest> deleteSingularityRequest(String requestId, Optional<SingularityDeleteRequestRequest> deleteRequest) {
      final Function<String, String> requestUri = (host) -> String.format(REQUEST_DELETE_ACTIVE_FORMAT, getApiBase(host), requestId);
  
      return delete(requestUri, "active request", requestId, deleteRequest, Optional.of(SingularityRequest.class));
    }
docs: Delete a singularity request.
  If the deletion is successful the singularity request is moved to a DELETING state and is returned.
  If the request to be deleted is not found {code Optional.absent()} is returned
  If an error occurs during deletion an exception is returned
  
  @param requestId
  the id of the singularity request to delete
  @return
  the singularity request that has been moved to deleting