Post a Rich-Text Feed Element with a Code Block

String communityId = null;
String targetUserOrGroupOrRecordId  = 'me';
String codeSnippet = '<html>\n\t<body>\n\t\tHello, world!\n\t</body>\n</html>';
ConnectApi.FeedItemInput input = new ConnectApi.FeedItemInput();
input.subjectId = targetUserOrGroupOrRecordId;
input.feedElementType = ConnectApi.FeedElementType.FeedItem;

ConnectApi.MessageBodyInput messageInput = new ConnectApi.MessageBodyInput();
ConnectApi.TextSegmentInput textSegment;
ConnectApi.MarkupBeginSegmentInput markupBeginSegment;
ConnectApi.MarkupEndSegmentInput markupEndSegment;

messageInput.messageSegments = new List<ConnectApi.MessageSegmentInput>();

markupBeginSegment = new ConnectApi.MarkupBeginSegmentInput();
markupBeginSegment.markupType = ConnectApi.MarkupType.Code;
messageInput.messageSegments.add(markupBeginSegment);

textSegment = new ConnectApi.TextSegmentInput();
textSegment.text = codeSnippet;
messageInput.messageSegments.add(textSegment);

markupEndSegment = new ConnectApi.MarkupEndSegmentInput();
markupEndSegment.markupType = ConnectApi.MarkupType.Code;
messageInput.messageSegments.add(markupEndSegment);

input.body = messageInput;

ConnectApi.ChatterFeeds.postFeedElement(communityId, input);