Enable SVG upload before Demo import

Hi,

I have some SVG images that I want to include with the import file.
So I need to enable the SVG upload before the import starts.
I tried using the before_content_import action and in it I add a filter to enable that, I think the filters don’t get applied at this point though as this doesn’t seem to work. How would I go about this? Thanks!

My code:

// Enable SVG upload for import
function upload_svg_mime_type($mimes) {
  $mimes['svg'] = 'image/svg+xml';
  return $mimes;
}
function my_before_content_import( $selected_import ) {
    add_filter('upload_mimes', 'upload_svg_mime_type');
}
add_action( 'pt-ocdi/before_content_import', 'my_before_content_import' );