title: How do I only show some nodes (edges) on graphviz and not others
body: <p>I have a very complex graph, and there is no way that I can show it all and understand it. I need to make simplified versions of it showing only some nodes and not others. I don't just want the other nodes to be invisible, but to really be absent (so that the graph is simplified). </p>
  
  <p>The solution would be to make a graph with only some layers. But is that possible? What other options are there?</p>
  
  <p>Thanks,
  Pietro</p>