    # File lib/supplemental/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