title: Groups of nodes with the same attributes in GraphViz file
body: <p>In the <code>dot</code> language of <a href="http://www.graphviz.org/" rel="noreferrer"><code>GraphViz</code></a> I want to describe a 2-mode network. So I have nodes of two different types.  One group for example could contains people how read and the other group could contain the books being read by the people.</p>
  
  <p>I want to give the nodes in these two  groups different looks (<code>shape</code>, <code>color</code>, etc). How can I specify the attributes <em>for a group of nodes</em> in one statement. The aim is to be able to change the look for each group of nodes in one place, not in all individual node descriptions.</p>
  
  <p>This could be done with something like <em>attribute inheritance</em>, but I don't know whether the <code>dot</code> language has this concept.</p>