# File lib/dm-core/model.rb, line 130
    def self.extended(model)
      descendants << model

      model.instance_variable_set(:@valid,         false)
      model.instance_variable_set(:@base_model,    model)
      model.instance_variable_set(:@storage_names, {})
      model.instance_variable_set(:@default_order, {})
      model.instance_variable_set(:@descendants,   descendants.class.new(model, descendants))

      extra_extensions.each { |mod| model.extend(mod)         }
      extra_inclusions.each { |mod| model.send(:include, mod) }
    end