declare! (Builder::XmlMarkup)

    # File lib/active_support/vendor/builder-2.1.2/builder/xmlmarkup.rb, line 208
        def declare!(inst, *args, &block)
          _indent
          @target << "<!#{inst}"
          args.each do |arg|
            case arg
            when String
              @target << %{ "#{arg}"} # " WART
            when Symbol
              @target << " #{arg}"
            end
          end
          if block_given?
            @target << " ["
            _newline
            _nested_structures(block)
            @target << "]"
          end
          @target << ">"
          _newline
        end