code: private void add(BitSet cycle) {
  
          BitSet intersect = and(cycle, cyclic);
  
          if (intersect.cardinality() > 1) {
              addFused(cycle);
          } else {
              addIsolated(cycle);
          }
  
          cyclic.or(cycle);
  
      }
docs: Add the cycle vertices to our discovered cycles. The cycle is first
  checked to see if it is isolated (shares at most one vertex) or
  <i>potentially</i> fused.
  
  @param cycle newly discovered cyclic vertex set