def merge_in(old)
      merge(@class_methods, old.class_methods)
      merge(@instance_methods, old.instance_methods)
      merge(@attributes, old.attributes)
      merge(@constants, old.constants)
      merge(@includes, old.includes)
      if @comment.nil? || @comment.empty?
        @comment = old.comment
      else
        unless old.comment.nil? or old.comment.empty? then
          @comment << SM::Flow::RULE.new
          @comment.concat old.comment
        end
      end
    end
def merge_in(old)
      merge(@class_methods, old.class_methods)
      merge(@instance_methods, old.instance_methods)
      merge(@attributes, old.attributes)
      merge(@constants, old.constants)
      merge(@includes, old.includes)
      if @comment.nil? || @comment.empty?
        @comment = old.comment
      else
        unless old.comment.nil? or old.comment.empty? then
          @comment << SM::Flow::RULE.new
          @comment.concat old.comment
        end
      end
    end
merge in another class desscription into this one