# File lib/mindi.rb, line 106
    def multikey_multiton(name, &impl) # :yields: arg0, arg1, ...
      impl_name = Container.impl_method_name(name)
      define_method(impl_name, &impl)

      ivname = Container.iv(name)
      define_method(name) do |*key|
        map = instance_variable_get(ivname)
        map ||= instance_variable_set(ivname, {})
        map[key] ||= send(impl_name, *key)
      end
    end