OptIn(vararg markerClass: KClass<out Annotation>)
Allows to use the API denoted by the given markers in the annotated file, declaration, or expression. If a declaration is annotated with OptIn, its usages are not required to opt in to that API.
markerClass specifies marker annotations that require explicit opt-in. The marker annotation is
not required to be itself marked with RequiresOptIn to enable gradual migration of API from requiring opt-in to the regular one,
yet declaring such
OptIn yields a compilation warning.
See also Kotlin language documentation for more information.