def set_value value, name=nil
      @value = value
      return unless @commands
      @commands.each_with_index do |comm, ix|
        comm.call(self, *@args[ix]) unless comm.nil?
      end
    end
def set_value value, name=nil
      @value = value
      return unless @commands
      @commands.each_with_index do |comm, ix|
        comm.call(self, *@args[ix]) unless comm.nil?
      end
    end
when a radio button is pressed, it calls set_value giving the value of that radio.
 it also gives the name (optionally) since Variables can also be passed and be used across
 groups. Here, since a button group is only for one group, so we discard name.
 @param [String] value (text) of radio button that is selected

 This is used by RadioButton class for backward compat with Variable.