code: function isAcyclic(g) {
    try {
      topsort(g);
    } catch (e) {
      if (e instanceof topsort.CycleException) return false;
      throw e;
    }
    return true;
  }
docs: /*
  Given a Digraph **g** this function returns `true` if the graph has no
  cycles and returns `false` if it does. This algorithm returns as soon as it
  detects the first cycle.
  
  Use [alg.findCycles][] if you need the actual list of cycles in a graph.
  
  [alg.findCycles]: findCycles.js.html#findCycles
  
  @param {Digraph} g the graph to test for cycles