#' @param object A \linkS4class{i2dash::i2dashboard} object.
#' @param cluster Values for the membership to clusters. In case of a nested list, a dropdown menu will be provided in the interactive mode.
#' @param x Numeric values mapped to the x-axis. In case of a nested list, a dropdown menu will be provided in the interactive mode. If x is NULL then a barplot for "Number of cells" per cluster will be created. If x is not NULL a barplot for "Fraction per cell" per cluster will be created.
#' @param title A title that will be displayed on top.
#'
#' @return A string containing markdown code for the rendered textbox
cluster_characterization_barplot<-function(object,x,cluster,title="Characterization of clusters"){