def ask_unselect prompt="Enter selection pattern: "
      ret = get_string prompt
      return if ret.nil? || ret ==  ""
      indices = get_matching_indices ret
      return if indices.nil? || indices.empty?
      indices.each { |e|
        # will not work if single select !! FIXME
        remove_row_selection_interval e,e
      }
    end
def ask_unselect prompt="Enter selection pattern: "
      ret = get_string prompt
      return if ret.nil? || ret ==  ""
      indices = get_matching_indices ret
      return if indices.nil? || indices.empty?
      indices.each { |e|
        # will not work if single select !! FIXME
        remove_row_selection_interval e,e
      }
    end
Asks user to enter a string or pattern for UNselecting rows
 UNSelects rows based on pattern, leaving other selections as-is