Borrowed text and functionality from par.
When parameters are set, their previous values are returned in an invisible named list.
Such a list can be passed as an argument to par to restore the parameter values. Use gconfig(no.readonly = TRUE)
for the full list of parameters that can be restored. When just one parameter is queried, the value of that
parameter is returned as (atomic) vector. When two or more parameters are queried, their values are returned
in a list, with the list names giving the parameters. Note the inconsistency: setting one parameter returns a list,
but querying one parameter returns a vector.