public function delete_duplicate($number_of_diseases, $first_surveillance_id, $malaria_data_id, $district, $epiweek, $year)
 {
     $last_surveillance_id = $first_surveillance_id + $number_of_diseases - 1;
     $surveillance_records = Surveillance::getSurveillanceDataRange($first_surveillance_id, $last_surveillance_id);
     foreach ($surveillance_records as $surveillance_record) {
         $surveillance_record->delete();
     }
     $lab_data = Lab_Weekly::getLabObjects($malaria_data_id);
     $lab_data->delete();
     $redirection_url = base_url() . "data_duplication/view_details/" . $epiweek . "/" . $year . "/" . $district;
     redirect($redirection_url);
 }