pre_get_posts for search results not working after activating plugin

Hi Team,

I have added one custom search form to search under a specific parent page and for that, I am adding a filter to manipulate query. But when I enable the solr plugin, I got results from the whole site instead of pages under a specific parent page.

/*
* Custom Search results
*/
function custom_searchfilter( $query ) {
	if ( $query->is_search){
		$query->set('solr_integrate', true);
	}

	if ( $query->is_search && isset( $_GET['search-type'] ) ) {
		$parent_page       = filter_input( INPUT_GET, 'search-type', FILTER_SANITIZE_STRING );
		$parent_page_array = explode( ', ', $parent_page );
		// print_r($parent_page_array);
		$query->set( 'post_parent__in', $parent_page_array );
		// $query->set( 'post_parent', 246 );
	}
	return $query;
}
add_filter( 'pre_get_posts', 'custom_searchfilter' );

I think plugin does not support the default filters of search.
Please suggest me a way to accomplish this.

Thanks