def marks(*names)
      return self if names.empty?
      names = names.flatten.collect { |n| n.to_s }
      self.select do |mark| 
        names.member? mark.name.to_s
      end
    end
def marks(*names)
      return self if names.empty?
      names = names.flatten.collect { |n| n.to_s }
      self.select do |mark| 
        names.member? mark.name.to_s
      end
    end
obj.marks(:execute_a, :execute_z, :do_request_a) =>
          [:execute_a, :do_request_a, :do_request_a, :execute_z]