Wordpress custom post type custom sorting column on backend

gistfile1.php

/* Sorting custom columns */

// Add new column in view
// quiz_answer  - post-type
add_filter('manage_quiz_answer_posts_columns', 'tankenbak_quiz_answer_table_head');
function tankenbak_quiz_answer_table_head( $defaults ) {
	$defaults['answers_points']  = __('Points', 'tankenbak');
	//$defaults['ticket_status']  = __('Status', 'tankenbak')
	return $defaults;
}

// Add value to column
add_action( 'manage_quiz_answer_posts_custom_column', 'tankenbak_quiz_answer_table_content', 10, 2 );
function tankenbak_quiz_answer_table_content( $column_name, $post_id ) {
	if ($column_name == 'answers_points') {
	$votes_count = get_post_meta( $post_id, 'answers_points', true );
	  echo  $votes_count;
	}
}

//add sorting option
add_filter( 'manage_edit-quiz_answer_sortable_columns', 'tankenbak_quiz_answer_table_sorting' );
function tankenbak_quiz_answer_table_sorting( $columns ) {
  $columns['answers_points'] = 'answers_points';
  return $columns;
}

// edit sorting to work on numbers
add_filter( 'request', 'tankenbak_quiz_answer_column_orderby' );
function tankenbak_quiz_answer_column_orderby( $vars ) {
	if ( isset( $vars['orderby'] ) && 'answers_points' == $vars['orderby'] ) {
		$vars = array_merge( $vars, array(
			'orderby' => 'meta_value_num',
			'meta_key' => 'answers_points',
		) );
	}

	return $vars;
}