once keyword ? [Vjass]

what is the syntax for use the once keyword for a library and a textmacro ?
It must be easy but i can't find it in the documentation

"The library_once keyword works exactly like library but you can declare the same library name twice, it would just ignore the second declaration and avoid to add its contents instead of showing a syntax error, it is useful in combination with textmacros."

"Hint: You can use textmacro_once in a similar way to library_once."

If your using opera you can search web pages with Ctrl+F. I'd assume that you can do the same with other browsers also.

i've read that but i believed that i must wrote like that :

instead of :


Because TESH don't consider it to a valid keyword. (for the style options i mean)
Sorry for this stupid question