code: protected function fieldShouldNotBeSaved($field, $value, $selectedFields)
      {
          $blacklistedFields = [
              'ID',
              'IBLOCK_ID',
              'GROUPS',
          ];
  
          return (!empty($selectedFields) && !in_array($field, $selectedFields))
              || in_array($field, $blacklistedFields)
              || ($field[0] === '~')
              || (substr($field, 0, 9) === 'PROPERTY_')
              || (is_array($this->original) && array_key_exists($field, $this->original) && $this->original[$field] === $value);
      }
docs: Determine whether the field should be stopped from passing to "update".
  
  @param string $field
  @param mixed  $value
  @param array  $selectedFields
  
  @return bool