title: Drawing a border around a set of vertices in Graphviz
body: <p>I am trying to draw a graph with Graphviz.</p>
  
  <p>I wish to draw a dotted line around a set of vertices, symbolizing that they are a part of a bigger entity.</p>
  
  <p>Say for example, if I have three vertices as eggs, chicken and ham, I should be able to draw a dotted line around all three of them, and label that border as food.</p>