Updating options from inputs

[Aariq]

For example, how would one implement a toggle to switch between light and dark mode? In bslib one can do something like the following in the server funciton:

observe({
    session$setCurrentTheme(
      if (input$dark_mode) {
        dark
      } else {
        light
      }
    )
  })

Is there an equivalent or some other way of updating the options argument dynamically?