function nishiki_pro_custom_archive_post_template( $file_path ){
    if( is_archive() ){
        $file_path = dirname(  FILE  ) . '/templates';
    }

    var_dump( $file_path );

    return $file_path;
}
add_filter( 'nishiki_pro_get_template_part_path_parts/archive/post', 'nishiki_pro_custom_archive_post_template' );

function nishiki_pro_custom_archive_post_template( $file_path ){
    if( is_archive() ){
        $file_path = dirname(  FILE  ) . '/templates';
    }

    var_dump( $file_path );

    return $file_path;
}
add_filter( 'nishiki_pro_get_template_part_path_parts/archive/post', 'nishiki_pro_custom_archive_post_template' );