[XML-SIG] Parameter entity visualization tool

[Hunting, Sam]

In python, is there such a thing as a parameter entity visualization tool,
that would show how content model "building blocks" work? This would seem to
be very useful in the context of understanding, maintaining, configuring,
extending DTDs/schemas like Voyager
(http://www.w3.org/TR/1998/WD-html-in-xml-19981205/) and of course the usual
suspects like TEI and docbook

<!ELEMENT (%paragraph.stuff)>

%paragraph.stuff
	#PCDATA
	| %this.stuff
		 a
		|b 
            | %that.stuff
		c
	           |d
            | %the.other.stuff
	          ""
I envision it working like a collapsible outliner, but a printout would be
fine too.