How to use the tab-set instruction?

[VForiel]

The documentation uses tab-set instructions, but they are not documented and I don't find how to use them

MyST-Parser/docs/syntax/optional.md

Lines 306 to 336 in 84c320b

	::::{tab-set}
	:::{tab-item} Markdown Input
	```md
	Inline: {{ key1 }}
	Block level:
	{{ key2 }}
	| col1 | col2 |
	| -------- | -------- |
	| {{key2}} | {{key3}} |
	```
	:::
	:::{tab-item} Rendered Output
	Inline: {{ key1 }}
	Block level:
	{{ key2 }}
	| col1 | col2 |
	| -------- | -------- |
	| {{key2}} | {{key3}} |
	:::
	::::

When I copy these instructions on my side it say that these instructions are unknown. Is it managed by another plugin? If so, which one?

[chrisjsewell]

Yep sphinx-design: https://sphinx-design.readthedocs.io/en/furo-theme/