#' If the last similar day has missing values, the next one is searched, and so on until
#' one full serie is found (if no one is found, NA is returned).
#'
+#' @usage f <- PersistenceForecaster$new(pjump)
+#'
#' @docType class
#' @format R6 class, inherits Forecaster
#' @aliases F_Persistence