check whether the current session is still authenticated
Source:R/liss_is_logged_in.R
liss_is_logged_in.Rdverifies the cached session by attempting to download a random data file
from the archive. returns FALSE if the session has expired or was
never established.
Examples
if (FALSE) { # \dontrun{
liss_login()
liss_is_logged_in()
} # }