#' @param obj [\code{character(1)} | \code{\link{Task}}]\cr
#'   Either a task or the type of the task, in the latter case one of:
#'   \dQuote{classif}, \dQuote{regr},  \dQuote{surv}, \dQuote{costsens}, \dQuote{cluster}, \dQuote{multilabel}.
#'   Default is \code{NA}, matching all types.
