def exists?(pos=nil)
      machines = pos.nil? ? list : get(pos)
      !machines.nil?
    end
def exists?(pos=nil)
      machines = pos.nil? ? list : get(pos)
      !machines.nil?
    end
def exists? ( pos = nil ) machines = pos . nil? ? list : get ( pos ) ! machines . nil? end
Returns true if any machine metadata exists for this group
Returns true if any machine metadata exists for this group