Support non-UTF-8 column headers in CSV template

Good evening. I have suggestions for function getTemplate(). I was faced with the header encoding. As they unloaded in UTF-8 Russian titles are not supported. I propose to do as follows,

  public function getTemplate() {
    $mappings = feeds_importer($this->id)->processor->config['mappings'];
    $sources = $uniques = array();
    $encoding = $this->config['encoding'];

    foreach ($mappings as $mapping) {
      if (in_array($mapping['source'], $uniques) || in_array($mapping['source'], $sources)) {
        // Skip columns we've already seen.
        continue;
      }

      if (!empty($mapping['unique'])) {
        $uniques[] = $mapping['source'];
      }
      else {
        $sources[] = $mapping['source'];
      }
    }

    $sep = $this->getDelimiterChar($this->config);
    $columns = array();

    foreach (array_merge($uniques, $sources) as $col) {
      if (strpos($col, $sep) !== FALSE) {
        $col = '"' . str_replace('"', '""', $col) . '"';
      }

      $columns[] = mb_convert_encoding($col, $encoding, 'utf-8');
    }

    $template_file_details = $this->getTemplateFileDetails($this->config);

    $filename = "{$this->id}_template.{$template_file_details['extension']}";
    $cache_control = 'max-age=60, must-revalidate';
    $content_disposition = 'attachment; filename="' . $filename . '"';
    $content_type = "{$template_file_details['mime_type']}; charset=utf-8";

    drupal_add_http_header('Cache-Control', $cache_control);
    drupal_add_http_header('Content-Disposition', $content_disposition);
    drupal_add_http_header('Content-type', $content_type);

    print implode($sep, $columns);
  }