private function get_metadata( $post_id ) {
		$metadata = get_metadata( 'post', $post_id );
		$items    = [];
		foreach ( $metadata as $key => $values ) {
			foreach ( $values as $item_value ) {
				$item_value    = maybe_unserialize( $item_value );
				$items[ $key ] = $item_value;
			}
		}

		return $items;
	}