Pasting HTML to TinyMCE?

[reox]

When using the TinyMCE editor, it is possible to copy formatted text and paste it with formatting into the editor.
I have a script that generates HTML code for the editor and I want to paste the rich text into the editor, rather than going to the source code tab and paste the raw HTML there.
Unfortunately, I cannot get this to work with klembord...

Here is a minimal example that takes an existing clipboard and just puts it again into the clipboard:

import klembord

klembord.init()
raw, rich = klembord.get_with_rich_text()
print(raw)
print(rich)
klembord.set_with_rich_text(raw, rich)

But if I paste then into the editor, I just see the raw text...

I further noticed that TinyMCE puts <!-- x-tinymce/html --> in front of the HTML content, and I tried that with simple examples such as:

import klembord
klembord.init()
klembord.set_with_rich_text('hello world', '<!-- x-tinymce/html -->hello <strong>world</strong>')

Which also does not work.

Is there something I do wrong, do I have to set the HTML code differently? Has anyone used klembord to paste stuff to TinyMCE?