how to orderby get_terms for wordpress taxonomy

public function pre_get_terms( $query ) {
        $meta_query_args = array(
            'relation' => 'AND', // Optional, defaults to "AND"
            array(
                'key'     => 'order_index',
                'value'   => 0,
                'compare' => '>='
            )
        );
        $meta_query = new WP_Meta_Query( $meta_query_args );
        $query->meta_query = $meta_query;
        $query->orderby = 'position_clause';
    }