def container=(arg)
      if arg.is_a?(EeePub::OCF::Container)
        @container = arg
      else
        # TODO: spec
        @container = EeePub::OCF::Container.new(arg)
      end
    end
def container=(arg)
      if arg.is_a?(EeePub::OCF::Container)
        @container = arg
      else
        # TODO: spec
        @container = EeePub::OCF::Container.new(arg)
      end
    end
@param [Hash<Symbol, Object>] values the values of symbols and objects for OCF

 @example
   EeePub::OCF.new(
     :dir => '/path/to/dir',
     :container => 'container.opf'
   )
 Set container

 @param [EeePub::OCF::Container or args for EeePub::OCF::Container]