public function get_order_notes( $order_id, $fields = null ) {

		// ensure ID is valid order ID
		$order_id = $this->validate_request( $order_id, $this->post_type, 'read' );

		if ( is_wp_error( $order_id ) ) {
			return $order_id;
		}

		$args = array(
			'post_id' => $order_id,
			'approve' => 'approve',
			'type'    => 'order_note',
		);

		remove_filter( 'comments_clauses', array( 'WC_Comments', 'exclude_order_comments' ), 10, 1 );

		$notes = get_comments( $args );

		add_filter( 'comments_clauses', array( 'WC_Comments', 'exclude_order_comments' ), 10, 1 );

		$order_notes = array();

		foreach ( $notes as $note ) {

			$order_notes[] = current( $this->get_order_note( $order_id, $note->comment_ID, $fields ) );
		}

		return array( 'order_notes' => apply_filters( 'woocommerce_api_order_notes_response', $order_notes, $order_id, $fields, $notes, $this->server ) );
	}