array_attribute (Gem::Specification)

    # File lib/rubygems/specification.rb, line 161
        def self.array_attribute(name)
          @@non_nil_attributes << ["@#{name}".intern, []]

          @@array_attributes << name
          @@attributes << [name, []]
          @@default_value[name] = []
          code = %{
            def #{name}
              @#{name} ||= []
            end
            def #{name}=(value)
              @#{name} = Array(value)
            end
          }

          module_eval code, __FILE__, __LINE__ - 9
        end