Limit SearchWP results to a specific post type

gistfile1.php

<?php
 
function my_searchwp_limit_to_post_type( $clause, $engine ) {
  global $wpdb;
  
  if ( isset( $_GET['post_type'] ) ) {
   $post_type = sanitize_text_field( $_GET['post_type'] );
   if ( post_type_exists( $post_type ) ) {
    $clause = $wpdb->prepare( "AND {$wpdb->prefix}posts.post_type = %s", $post_type );
   }
  }
  
  return $clause;
}
 
add_filter( 'searchwp_where', 'my_searchwp_limit_to_post_type', 10, 2 );