# File lib/more/facets/multiton.rb, line 215
    def instance(*e, &b)
      arg = multiton_id(*e, &b)
      multiton_instance.fetch(arg) do
        multiton_mutex[arg].synchronize do
          multiton_instance.fetch(arg) do
            val = multiton_instance[arg] = new!(*e, &b) #new(*e, &b)
            val.instance_variable_set(:@multiton_initializer, e, &b)
            multiton_mutex.initialized(arg)
            val
          end
        end
      end
    end