RSelenium findElement

I want to find out the class name for the search tab on

I wrote the following code

rs <- rsDriver()
rsc <- rs$client
rsc$navigate(" ")
element <- rsc$findElement('class name','.ng-pristine ng-empty ng-valid ng-valid-required flex ng-touched')

for which I got the following error for the 4th line

Error: Summary: NoSuchDriver|
Detail: A session is either terminated or not started|