User = Meta.new do
  validates_presence_of :login
  def ping ; :pong ; end
end
    # ==> User
MyUser = Meta.new { implements User }
    # ==> MyUser
u = MyUser.new
    # ==> #<MyUser uuid: "4245be7a-235f-4477-b3b4-84015cff36b7", version: 0000...>
u.valid?
    # ==> false
u.errors.messages
    # ==> ["User's login should be present on save"]
u.ping
    # ==> :pong