title: How to create vertices on the fly based on the labels of edges in OCaml?
body: <p>I am trying to solve LTS(Labelled Transition System) using OCaml.
  I have edges with labels on them and source of the edges. Now I want to create the destination of the edge whose name depends on the source and label of the edge.</p>
  
  <p>I not very fluent with OCaml, so please elaborate your answers.</p>